Merge pull request #588 from flowln/mod_update

Implement mod updater (😎)

CMakeLists.txt

@@ -323,6 +323,7 @@ add_subdirectory(libraries/optional-bare)
 add_subdirectory(libraries/tomlc99) # toml parser
 add_subdirectory(libraries/katabasis) # An OAuth2 library that tried to do too much
 add_subdirectory(libraries/gamemode)
+add_subdirectory(libraries/murmur2) # Hash for usage with the CurseForge API
 
 ############################### Built Artifacts ###############################
 

launcher/CMakeLists.txt

@@ -397,6 +397,8 @@ set(TASKS_SOURCES
     tasks/ConcurrentTask.cpp
     tasks/SequentialTask.h
     tasks/SequentialTask.cpp
+    tasks/MultipleOptionsTask.h
+    tasks/MultipleOptionsTask.cpp
 )
 
 ecm_add_test(tasks/Task_test.cpp LINK_LIBRARIES Launcher_logic Qt${QT_VERSION_MAJOR}::Test
@@ -480,9 +482,15 @@ set(API_SOURCES
 
     modplatform/ModAPI.h
 
-    modplatform/flame/FlameAPI.h
+    modplatform/EnsureMetadataTask.h
-    modplatform/modrinth/ModrinthAPI.h
+    modplatform/EnsureMetadataTask.cpp
 
+    modplatform/CheckUpdateTask.h
+
+    modplatform/flame/FlameAPI.h
+    modplatform/flame/FlameAPI.cpp
+    modplatform/modrinth/ModrinthAPI.h
+    modplatform/modrinth/ModrinthAPI.cpp
     modplatform/helpers/NetworkModAPI.h
     modplatform/helpers/NetworkModAPI.cpp
 )
@@ -508,6 +516,8 @@ set(FLAME_SOURCES
     modplatform/flame/PackManifest.cpp
     modplatform/flame/FileResolvingTask.h
     modplatform/flame/FileResolvingTask.cpp
+    modplatform/flame/FlameCheckUpdate.cpp
+    modplatform/flame/FlameCheckUpdate.h
 )
 
 set(MODRINTH_SOURCES
@@ -515,6 +525,8 @@ set(MODRINTH_SOURCES
     modplatform/modrinth/ModrinthPackIndex.h
     modplatform/modrinth/ModrinthPackManifest.cpp
     modplatform/modrinth/ModrinthPackManifest.h
+    modplatform/modrinth/ModrinthCheckUpdate.cpp
+    modplatform/modrinth/ModrinthCheckUpdate.h
 )
 
 set(MODPACKSCH_SOURCES
@@ -836,6 +848,10 @@ SET(LAUNCHER_SOURCES
     ui/dialogs/ModDownloadDialog.h
     ui/dialogs/ScrollMessageBox.cpp
     ui/dialogs/ScrollMessageBox.h
+    ui/dialogs/ChooseProviderDialog.h
+    ui/dialogs/ChooseProviderDialog.cpp
+    ui/dialogs/ModUpdateDialog.cpp
+    ui/dialogs/ModUpdateDialog.h
 
     # GUI - widgets
     ui/widgets/Common.cpp
@@ -941,6 +957,7 @@ qt_wrap_ui(LAUNCHER_UI
     ui/dialogs/EditAccountDialog.ui
     ui/dialogs/ReviewMessageBox.ui
     ui/dialogs/ScrollMessageBox.ui
+    ui/dialogs/ChooseProviderDialog.ui
 )
 
 qt_add_resources(LAUNCHER_RESOURCES
@@ -967,6 +984,7 @@ add_library(Launcher_logic STATIC ${LOGIC_SOURCES} ${LAUNCHER_SOURCES} ${LAUNCHE
 target_link_libraries(Launcher_logic
     systeminfo
     Launcher_classparser
+    Launcher_murmur2
     nbt++
     ${ZLIB_LIBRARIES}
     optional-bare

launcher/MMCZip.cpp

@@ -127,7 +127,7 @@ bool MMCZip::compressDirFiles(QString fileCompressed, QString dir, QFileInfoList
 }
 
 // ours
-bool MMCZip::createModdedJar(QString sourceJarPath, QString targetJarPath, const QList<Mod>& mods)
+bool MMCZip::createModdedJar(QString sourceJarPath, QString targetJarPath, const QList<Mod*>& mods)
 {
     QuaZip zipOut(targetJarPath);
     if (!zipOut.open(QuaZip::mdCreate))
@@ -141,42 +141,40 @@ bool MMCZip::createModdedJar(QString sourceJarPath, QString targetJarPath, const
     QSet<QString> addedFiles;
 
     // Modify the jar
-    QListIterator<Mod> i(mods);
+    for (auto i = mods.constEnd(); i != mods.constBegin(); --i)
-    i.toBack();
-    while (i.hasPrevious())
     {
-        const Mod &mod = i.previous();
+        const Mod* mod = *i;
         // do not merge disabled mods.
-        if (!mod.enabled())
+        if (!mod->enabled())
             continue;
-        if (mod.type() == Mod::MOD_ZIPFILE)
+        if (mod->type() == Mod::MOD_ZIPFILE)
         {
-            if (!mergeZipFiles(&zipOut, mod.fileinfo(), addedFiles))
+            if (!mergeZipFiles(&zipOut, mod->fileinfo(), addedFiles))
             {
                 zipOut.close();
                 QFile::remove(targetJarPath);
-                qCritical() << "Failed to add" << mod.fileinfo().fileName() << "to the jar.";
+                qCritical() << "Failed to add" << mod->fileinfo().fileName() << "to the jar.";
                 return false;
             }
         }
-        else if (mod.type() == Mod::MOD_SINGLEFILE)
+        else if (mod->type() == Mod::MOD_SINGLEFILE)
         {
             // FIXME: buggy - does not work with addedFiles
-            auto filename = mod.fileinfo();
+            auto filename = mod->fileinfo();
             if (!JlCompress::compressFile(&zipOut, filename.absoluteFilePath(), filename.fileName()))
             {
                 zipOut.close();
                 QFile::remove(targetJarPath);
-                qCritical() << "Failed to add" << mod.fileinfo().fileName() << "to the jar.";
+                qCritical() << "Failed to add" << mod->fileinfo().fileName() << "to the jar.";
                 return false;
             }
             addedFiles.insert(filename.fileName());
         }
-        else if (mod.type() == Mod::MOD_FOLDER)
+        else if (mod->type() == Mod::MOD_FOLDER)
         {
             // untested, but seems to be unused / not possible to reach
             // FIXME: buggy - does not work with addedFiles
-            auto filename = mod.fileinfo();
+            auto filename = mod->fileinfo();
             QString what_to_zip = filename.absoluteFilePath();
             QDir dir(what_to_zip);
             dir.cdUp();
@@ -193,7 +191,7 @@ bool MMCZip::createModdedJar(QString sourceJarPath, QString targetJarPath, const
             {
                 zipOut.close();
                 QFile::remove(targetJarPath);
-                qCritical() << "Failed to add" << mod.fileinfo().fileName() << "to the jar.";
+                qCritical() << "Failed to add" << mod->fileinfo().fileName() << "to the jar.";
                 return false;
             }
             qDebug() << "Adding folder " << filename.fileName() << " from "
@@ -204,7 +202,7 @@ bool MMCZip::createModdedJar(QString sourceJarPath, QString targetJarPath, const
             // Make sure we do not continue launching when something is missing or undefined...
             zipOut.close();
             QFile::remove(targetJarPath);
-            qCritical() << "Failed to add unknown mod type" << mod.fileinfo().fileName() << "to the jar.";
+            qCritical() << "Failed to add unknown mod type" << mod->fileinfo().fileName() << "to the jar.";
             return false;
         }
     }

launcher/MMCZip.h

@@ -75,7 +75,7 @@ namespace MMCZip
     /**
      * take a source jar, add mods to it, resulting in target jar
      */
-    bool createModdedJar(QString sourceJarPath, QString targetJarPath, const QList<Mod>& mods);
+    bool createModdedJar(QString sourceJarPath, QString targetJarPath, const QList<Mod*>& mods);
 
     /**
      * Find a single file in archive by file name (not path)

launcher/ModDownloadTask.cpp

@@ -27,6 +27,7 @@ ModDownloadTask::ModDownloadTask(ModPlatform::IndexedPack mod, ModPlatform::Inde
 {
     if (is_indexed) {
         m_update_task.reset(new LocalModUpdateTask(mods->indexDir(), m_mod, m_mod_version));
+        connect(m_update_task.get(), &LocalModUpdateTask::hasOldMod, this, &ModDownloadTask::hasOldMod);
 
         addTask(m_update_task);
     }
@@ -40,12 +41,16 @@ ModDownloadTask::ModDownloadTask(ModPlatform::IndexedPack mod, ModPlatform::Inde
     connect(m_filesNetJob.get(), &NetJob::failed, this, &ModDownloadTask::downloadFailed);
 
     addTask(m_filesNetJob);
-
 }
 
 void ModDownloadTask::downloadSucceeded()
 {
     m_filesNetJob.reset();
+    auto name = std::get<0>(to_delete);
+    auto filename = std::get<1>(to_delete);
+    if (!name.isEmpty() && filename != m_mod_version.fileName) {
+        mods->uninstallMod(filename, true);
+    }
 }
 
 void ModDownloadTask::downloadFailed(QString reason)
@@ -58,3 +63,10 @@ void ModDownloadTask::downloadProgressChanged(qint64 current, qint64 total)
 {
     emit progress(current, total);
 }
+
+// This indirection is done so that we don't delete a mod before being sure it was
+// downloaded successfully!
+void ModDownloadTask::hasOldMod(QString name, QString filename)
+{
+    to_delete = {name, filename};
+}

launcher/ModDownloadTask.h

@@ -30,7 +30,7 @@ class ModFolderModel;
 class ModDownloadTask : public SequentialTask {
     Q_OBJECT
 public:
-    explicit ModDownloadTask(ModPlatform::IndexedPack mod, ModPlatform::IndexedVersion version, const std::shared_ptr<ModFolderModel> mods, bool is_indexed);
+    explicit ModDownloadTask(ModPlatform::IndexedPack mod, ModPlatform::IndexedVersion version, const std::shared_ptr<ModFolderModel> mods, bool is_indexed = true);
     const QString& getFilename() const { return m_mod_version.fileName; }
 
 private:
@@ -46,6 +46,11 @@ private:
     void downloadFailed(QString reason);
 
     void downloadSucceeded();
+
+    std::tuple<QString, QString> to_delete {"", ""};
+
+private slots:
+    void hasOldMod(QString name, QString filename);
 };
 
 

launcher/minecraft/MinecraftInstance.cpp

@@ -700,24 +700,24 @@ QStringList MinecraftInstance::verboseDescription(AuthSessionPtr session, Minecr
         {
             out << QString("%1:").arg(label);
             auto modList = model.allMods();
-            std::sort(modList.begin(), modList.end(), [](Mod &a, Mod &b) {
+            std::sort(modList.begin(), modList.end(), [](Mod::Ptr a, Mod::Ptr b) {
-                auto aName = a.fileinfo().completeBaseName();
+                auto aName = a->fileinfo().completeBaseName();
-                auto bName = b.fileinfo().completeBaseName();
+                auto bName = b->fileinfo().completeBaseName();
                 return aName.localeAwareCompare(bName) < 0;
             });
-            for(auto & mod: modList)
+            for(auto mod: modList)
             {
-                if(mod.type() == Mod::MOD_FOLDER)
+                if(mod->type() == Mod::MOD_FOLDER)
                 {
-                    out << u8"  [📁] " + mod.fileinfo().completeBaseName() + " (folder)";
+                    out << u8"  [📁] " + mod->fileinfo().completeBaseName() + " (folder)";
                     continue;
                 }
 
-                if(mod.enabled()) {
+                if(mod->enabled()) {
-                    out << u8"  [✔️] " + mod.fileinfo().completeBaseName();
+                    out << u8"  [✔️]" + mod->fileinfo().completeBaseName();
                 }
                 else {
-                    out << u8"  [❌] " + mod.fileinfo().completeBaseName() + " (disabled)";
+                    out << u8"  [❌] " + mod->fileinfo().completeBaseName() + " (disabled)";
                 }
 
             }
@@ -1136,16 +1136,16 @@ std::shared_ptr<GameOptions> MinecraftInstance::gameOptionsModel() const
     return m_game_options;
 }
 
-QList< Mod > MinecraftInstance::getJarMods() const
+QList<Mod*> MinecraftInstance::getJarMods() const
 {
     auto profile = m_components->getProfile();
-    QList<Mod> mods;
+    QList<Mod*> mods;
     for (auto jarmod : profile->getJarMods())
     {
         QStringList jar, temp1, temp2, temp3;
         jarmod->getApplicableFiles(currentSystem, jar, temp1, temp2, temp3, jarmodsPath().absolutePath());
         // QString filePath = jarmodsPath().absoluteFilePath(jarmod->filename(currentSystem));
-        mods.push_back(Mod(QFileInfo(jar[0])));
+        mods.push_back(new Mod(QFileInfo(jar[0])));
     }
     return mods;
 }

launcher/minecraft/MinecraftInstance.h

@@ -81,7 +81,7 @@ public:
     shared_qobject_ptr<LaunchTask> createLaunchTask(AuthSessionPtr account, MinecraftServerTargetPtr serverToJoin) override;
     QStringList extraArguments() const override;
     QStringList verboseDescription(AuthSessionPtr session, MinecraftServerTargetPtr serverToJoin) override;
-    QList<Mod> getJarMods() const;
+    QList<Mod*> getJarMods() const;
     QString createLaunchScript(AuthSessionPtr session, MinecraftServerTargetPtr serverToJoin);
     /// get arguments passed to java
     QStringList javaArguments() const;

launcher/minecraft/mod/MetadataHandler.h

@@ -37,9 +37,9 @@ class Metadata {
         return Packwiz::V1::createModFormat(index_dir, mod_pack, mod_version);
     }
 
-    static auto create(QDir& index_dir, Mod& internal_mod) -> ModStruct
+    static auto create(QDir& index_dir, Mod& internal_mod, QString mod_slug) -> ModStruct
     {
-        return Packwiz::V1::createModFormat(index_dir, internal_mod);
+        return Packwiz::V1::createModFormat(index_dir, internal_mod, mod_slug);
     }
 
     static void update(QDir& index_dir, ModStruct& mod)
@@ -47,13 +47,23 @@ class Metadata {
         Packwiz::V1::updateModIndex(index_dir, mod);
     }
 
-    static void remove(QDir& index_dir, QString& mod_name)
+    static void remove(QDir& index_dir, QString mod_slug)
     {
-        Packwiz::V1::deleteModIndex(index_dir, mod_name);
+        Packwiz::V1::deleteModIndex(index_dir, mod_slug);
     }
 
-    static auto get(QDir& index_dir, QString& mod_name) -> ModStruct
+    static void remove(QDir& index_dir, QVariant& mod_id)
     {
-        return Packwiz::V1::getIndexForMod(index_dir, mod_name);
+        Packwiz::V1::deleteModIndex(index_dir, mod_id);
+    }
+
+    static auto get(QDir& index_dir, QString mod_slug) -> ModStruct
+    {
+        return Packwiz::V1::getIndexForMod(index_dir, mod_slug);
+    }
+
+    static auto get(QDir& index_dir, QVariant& mod_id) -> ModStruct
+    {
+        return Packwiz::V1::getIndexForMod(index_dir, mod_id);
     }
 };

launcher/minecraft/mod/Mod.cpp

@@ -150,25 +150,30 @@ void Mod::setStatus(ModStatus status)
         m_temp_status = status;
     }
 }
-void Mod::setMetadata(Metadata::ModStruct* metadata)
+void Mod::setMetadata(const Metadata::ModStruct& metadata)
 {
     if (status() == ModStatus::NoMetadata)
         setStatus(ModStatus::Installed);
 
     if (m_localDetails) {
-        m_localDetails->metadata.reset(metadata);
+        m_localDetails->metadata = std::make_shared<Metadata::ModStruct>(std::move(metadata));
     } else {
-        m_temp_metadata.reset(metadata);
+        m_temp_metadata = std::make_shared<Metadata::ModStruct>(std::move(metadata));
     }
 }
 
-auto Mod::destroy(QDir& index_dir) -> bool
+auto Mod::destroy(QDir& index_dir, bool preserve_metadata) -> bool
 {
-    auto n = name();
+    if (!preserve_metadata) {
-    // FIXME: This can fail to remove the metadata if the
+        qDebug() << QString("Destroying metadata for '%1' on purpose").arg(name());
-    // "ModMetadataDisabled" setting is on, since there could
+
-    // be a name mismatch!
+        if (metadata()) {
-    Metadata::remove(index_dir, n);
+            Metadata::remove(index_dir, metadata()->slug);
+        } else {
+            auto n = name();
+            Metadata::remove(index_dir, n);
+        }
+    }
 
     m_type = MOD_UNKNOWN;
     return FS::deletePath(m_file.filePath());
@@ -182,9 +187,12 @@ auto Mod::details() const -> const ModDetails&
 auto Mod::name() const -> QString
 {
     auto d_name = details().name;
-    if (!d_name.isEmpty()) {
+    if (!d_name.isEmpty())
         return d_name;
-    }
+
+    if (metadata())
+        return metadata()->name;
+
     return m_name;
 }
 
@@ -235,11 +243,10 @@ void Mod::finishResolvingWithDetails(std::shared_ptr<ModDetails> details)
     m_resolved = true;
     m_localDetails = details;
 
-    if (m_localDetails && m_temp_metadata && m_temp_metadata->isValid()) {
-        m_localDetails->metadata = m_temp_metadata;
-        if (status() == ModStatus::NoMetadata)
-            setStatus(ModStatus::Installed);
-    }
-
     setStatus(m_temp_status);
+
+    if (m_localDetails && m_temp_metadata && m_temp_metadata->isValid()) {
+        setMetadata(*m_temp_metadata);
+        m_temp_metadata.reset();
+    }
 }

launcher/minecraft/mod/Mod.h

@@ -39,10 +39,12 @@
 #include <QFileInfo>
 #include <QList>
 
+#include "QObjectPtr.h"
 #include "ModDetails.h"
 
-class Mod
+class Mod : public QObject
 {
+    Q_OBJECT
 public:
     enum ModType
     {
@@ -53,6 +55,8 @@ public:
         MOD_LITEMOD,    //!< The mod is a litemod
     };
 
+    using Ptr = shared_qobject_ptr<Mod>;
+
     Mod() = default;
     Mod(const QFileInfo &file);
     explicit Mod(const QDir& mods_dir, const Metadata::ModStruct& metadata);
@@ -77,12 +81,12 @@ public:
     auto metadata() const -> const std::shared_ptr<Metadata::ModStruct>;
 
     void setStatus(ModStatus status);
-    void setMetadata(Metadata::ModStruct* metadata);
+    void setMetadata(const Metadata::ModStruct& metadata);
 
     auto enable(bool value) -> bool;
 
     // delete all the files of this mod
-    auto destroy(QDir& index_dir) -> bool;
+    auto destroy(QDir& index_dir, bool preserve_metadata = false) -> bool;
 
     // change the mod's filesystem path (used by mod lists for *MAGIC* purposes)
     void repath(const QFileInfo &file);
@@ -111,7 +115,7 @@ protected:
     std::shared_ptr<Metadata::ModStruct> m_temp_metadata;
 
     /* Set the mod status while it doesn't have local details just yet */
-    ModStatus m_temp_status = ModStatus::NotInstalled;
+    ModStatus m_temp_status = ModStatus::NoMetadata;
 
     std::shared_ptr<ModDetails> m_localDetails;
 

launcher/minecraft/mod/ModFolderModel.cpp

@@ -65,15 +65,21 @@ void ModFolderModel::startWatching()
 
     update();
 
+    // Watch the mods folder
     is_watching = m_watcher->addPath(m_dir.absolutePath());
-    if (is_watching)
+    if (is_watching) {
-    {
         qDebug() << "Started watching " << m_dir.absolutePath();
-    }
+    } else {
-    else
-    {
         qDebug() << "Failed to start watching " << m_dir.absolutePath();
     }
+
+    // Watch the mods index folder
+    is_watching = m_watcher->addPath(indexDir().absolutePath());
+    if (is_watching) {
+        qDebug() << "Started watching " << indexDir().absolutePath();
+    } else {
+        qDebug() << "Failed to start watching " << indexDir().absolutePath();
+    }
 }
 
 void ModFolderModel::stopWatching()
@@ -82,14 +88,18 @@ void ModFolderModel::stopWatching()
         return;
 
     is_watching = !m_watcher->removePath(m_dir.absolutePath());
-    if (!is_watching)
+    if (!is_watching) {
-    {
         qDebug() << "Stopped watching " << m_dir.absolutePath();
-    }
+    } else {
-    else
-    {
         qDebug() << "Failed to stop watching " << m_dir.absolutePath();
     }
+
+    is_watching = !m_watcher->removePath(indexDir().absolutePath());
+    if (!is_watching) {
+        qDebug() << "Stopped watching " << indexDir().absolutePath();
+    } else {
+        qDebug() << "Failed to stop watching " << indexDir().absolutePath();
+    }
 }
 
 bool ModFolderModel::update()
@@ -124,7 +134,7 @@ void ModFolderModel::finishUpdate()
     QSet<QString> newSet(newList.begin(), newList.end());
 #else
     QSet<QString> currentSet = modsIndex.keys().toSet();
-    auto & newMods = m_update->mods;
+    auto& newMods = m_update->mods;
     QSet<QString> newSet = newMods.keys().toSet();
 #endif
 
@@ -132,19 +142,20 @@ void ModFolderModel::finishUpdate()
     {
         QSet<QString> kept = currentSet;
         kept.intersect(newSet);
-        for(auto & keptMod: kept) {
+        for(auto& keptMod : kept) {
-            auto & newMod = newMods[keptMod];
+            auto newMod = newMods[keptMod];
             auto row = modsIndex[keptMod];
-            auto & currentMod = mods[row];
+            auto currentMod = mods[row];
-            if(newMod.dateTimeChanged() == currentMod.dateTimeChanged()) {
+            if(newMod->dateTimeChanged() == currentMod->dateTimeChanged()) {
                 // no significant change, ignore...
                 continue;
             }
-            auto & oldMod = mods[row];
+            auto oldMod = mods[row];
-            if(oldMod.isResolving()) {
+            if(oldMod->isResolving()) {
-                activeTickets.remove(oldMod.resolutionTicket());
+                activeTickets.remove(oldMod->resolutionTicket());
             }
-            oldMod = newMod;
+
+            mods[row] = newMod;
             resolveMod(mods[row]);
             emit dataChanged(index(row, 0), index(row, columnCount(QModelIndex()) - 1));
         }
@@ -163,9 +174,10 @@ void ModFolderModel::finishUpdate()
             int removedIndex = *iter;
             beginRemoveRows(QModelIndex(), removedIndex, removedIndex);
             auto removedIter = mods.begin() + removedIndex;
-            if(removedIter->isResolving()) {
+            if((*removedIter)->isResolving()) {
-                activeTickets.remove(removedIter->resolutionTicket());
+                activeTickets.remove((*removedIter)->resolutionTicket());
             }
+
             mods.erase(removedIter);
             endRemoveRows();
         }
@@ -191,8 +203,8 @@ void ModFolderModel::finishUpdate()
     {
         modsIndex.clear();
         int idx = 0;
-        for(auto & mod: mods) {
+        for(auto mod: mods) {
-            modsIndex[mod.internal_id()] = idx;
+            modsIndex[mod->internal_id()] = idx;
             idx++;
         }
     }
@@ -207,17 +219,17 @@ void ModFolderModel::finishUpdate()
     }
 }
 
-void ModFolderModel::resolveMod(Mod& m)
+void ModFolderModel::resolveMod(Mod::Ptr m)
 {
-    if(!m.shouldResolve()) {
+    if(!m->shouldResolve()) {
         return;
     }
 
-    auto task = new LocalModParseTask(nextResolutionTicket, m.type(), m.fileinfo());
+    auto task = new LocalModParseTask(nextResolutionTicket, m->type(), m->fileinfo());
     auto result = task->result();
-    result->id = m.internal_id();
+    result->id = m->internal_id();
     activeTickets.insert(nextResolutionTicket, result);
-    m.setResolving(true, nextResolutionTicket);
+    m->setResolving(true, nextResolutionTicket);
     nextResolutionTicket++;
     QThreadPool *threadPool = QThreadPool::globalInstance();
     connect(task, &LocalModParseTask::finished, this, &ModFolderModel::finishModParse);
@@ -233,8 +245,8 @@ void ModFolderModel::finishModParse(int token)
     auto result = *iter;
     activeTickets.remove(token);
     int row = modsIndex[result->id];
-    auto & mod = mods[row];
+    auto mod = mods[row];
-    mod.finishResolvingWithDetails(result->details);
+    mod->finishResolvingWithDetails(result->details);
     emit dataChanged(index(row), index(row, columnCount(QModelIndex()) - 1));
 }
 
@@ -259,6 +271,18 @@ bool ModFolderModel::isValid()
     return m_dir.exists() && m_dir.isReadable();
 }
 
+auto ModFolderModel::selectedMods(QModelIndexList& indexes) -> QList<Mod::Ptr>
+{
+    QList<Mod::Ptr> selected_mods;
+    for (auto i : indexes) {
+        if(i.column() != 0)
+            continue;
+
+        selected_mods.push_back(mods[i.row()]);
+    }
+    return selected_mods;
+}
+
 // FIXME: this does not take disabled mod (with extra .disable extension) into account...
 bool ModFolderModel::installMod(const QString &filename)
 {
@@ -344,6 +368,20 @@ bool ModFolderModel::installMod(const QString &filename)
     return false;
 }
 
+bool ModFolderModel::uninstallMod(const QString& filename, bool preserve_metadata)
+{
+
+    for(auto mod : allMods()){
+        if(mod->fileinfo().fileName() == filename){
+            auto index_dir = indexDir();
+            mod->destroy(index_dir, preserve_metadata);
+            return true;
+        }
+    }
+
+    return false;
+}
+
 bool ModFolderModel::setModStatus(const QModelIndexList& indexes, ModStatusAction enable)
 {
     if(interaction_disabled) {
@@ -377,9 +415,9 @@ bool ModFolderModel::deleteMods(const QModelIndexList& indexes)
         if(i.column() != 0) {
             continue;
         }
-        Mod &m = mods[i.row()];
+        auto m = mods[i.row()];
         auto index_dir = indexDir();
-        m.destroy(index_dir);
+        m->destroy(index_dir);
     }
     return true;
 }
@@ -406,9 +444,9 @@ QVariant ModFolderModel::data(const QModelIndex &index, int role) const
         switch (column)
         {
         case NameColumn:
-            return mods[row].name();
+            return mods[row]->name();
         case VersionColumn: {
-            switch(mods[row].type()) {
+            switch(mods[row]->type()) {
                 case Mod::MOD_FOLDER:
                     return tr("Folder");
                 case Mod::MOD_SINGLEFILE:
@@ -416,23 +454,23 @@ QVariant ModFolderModel::data(const QModelIndex &index, int role) const
                 default:
                     break;
             }
-            return mods[row].version();
+            return mods[row]->version();
         }
         case DateColumn:
-            return mods[row].dateTimeChanged();
+            return mods[row]->dateTimeChanged();
 
         default:
             return QVariant();
         }
 
     case Qt::ToolTipRole:
-        return mods[row].internal_id();
+        return mods[row]->internal_id();
 
     case Qt::CheckStateRole:
         switch (column)
         {
         case ActiveColumn:
-            return mods[row].enabled() ? Qt::Checked : Qt::Unchecked;
+            return mods[row]->enabled() ? Qt::Checked : Qt::Unchecked;
         default:
             return QVariant();
         }
@@ -472,20 +510,20 @@ bool ModFolderModel::setModStatus(int row, ModFolderModel::ModStatusAction actio
             break;
         case Toggle:
         default:
-            desiredStatus = !mod.enabled();
+            desiredStatus = !mod->enabled();
             break;
     }
 
-    if(desiredStatus == mod.enabled()) {
+    if(desiredStatus == mod->enabled()) {
         return true;
     }
 
     // preserve the row, but change its ID
-    auto oldId = mod.internal_id();
+    auto oldId = mod->internal_id();
-    if(!mod.enable(!mod.enabled())) {
+    if(!mod->enable(!mod->enabled())) {
         return false;
     }
-    auto newId = mod.internal_id();
+    auto newId = mod->internal_id();
     if(modsIndex.contains(newId)) {
         // NOTE: this could handle a corner case, where we are overwriting a file, because the same 'mod' exists both enabled and disabled
         // But is it necessary?

launcher/minecraft/mod/ModFolderModel.h

@@ -101,13 +101,13 @@ public:
     {
         return size() == 0;
     }
-    Mod &operator[](size_t index)
+    Mod& operator[](size_t index)
     {
-        return mods[index];
+        return *mods[index];
     }
-    const Mod &at(size_t index) const
+    const Mod& at(size_t index) const
     {
-        return mods.at(index);
+        return *mods.at(index);
     }
 
     /// Reloads the mod list and returns true if the list changed.
@@ -118,6 +118,8 @@ public:
      */
     bool installMod(const QString& filename);
 
+    bool uninstallMod(const QString& filename, bool preserve_metadata = false);
+
     /// Deletes all the selected mods
     bool deleteMods(const QModelIndexList &indexes);
 
@@ -139,11 +141,13 @@ public:
         return { QString("%1/.index").arg(dir().absolutePath()) };
     }
 
-    const QList<Mod> & allMods()
+    const QList<Mod::Ptr>& allMods()
     {
         return mods;
     }
 
+    auto selectedMods(QModelIndexList& indexes) -> QList<Mod::Ptr>;
+
 public slots:
     void disableInteraction(bool disabled);
 
@@ -157,7 +161,7 @@ signals:
     void updateFinished();
 
 private:
-    void resolveMod(Mod& m);
+    void resolveMod(Mod::Ptr m);
     bool setModStatus(int index, ModStatusAction action);
 
 protected:
@@ -171,5 +175,5 @@ protected:
     QMap<QString, int> modsIndex;
     QMap<int, LocalModParseTask::ResultPtr> activeTickets;
     int nextResolutionTicket = 0;
-    QList<Mod> mods;
+    QList<Mod::Ptr> mods;
 };

launcher/minecraft/mod/tasks/LocalModParseTask.cpp

@@ -4,6 +4,7 @@
 #include <QJsonObject>
 #include <QJsonArray>
 #include <QJsonValue>
+#include <QString>
 #include <quazip/quazip.h>
 #include <quazip/quazipfile.h>
 #include <toml.h>
@@ -71,7 +72,13 @@ std::shared_ptr<ModDetails> ReadMCModInfo(QByteArray contents)
         if(val.isUndefined()) {
             val = jsonDoc.object().value("modListVersion");
         }
-        int version = val.toDouble();
+
+        int version = Json::ensureInteger(val, -1);
+
+        // Some mods set the number with "", so it's a String instead
+        if (version < 0)
+            version = Json::ensureString(val, "").toInt();
+
         if (version != 2)
         {
             qCritical() << "BAD stuff happened to mod json:";

launcher/minecraft/mod/tasks/LocalModUpdateTask.cpp

@@ -44,10 +44,21 @@ void LocalModUpdateTask::executeTask()
 {
     setStatus(tr("Updating index for mod:\n%1").arg(m_mod.name));
 
-    auto pw_mod = Metadata::create(m_index_dir, m_mod, m_mod_version);
+    auto old_metadata = Metadata::get(m_index_dir, m_mod.addonId);
-    Metadata::update(m_index_dir, pw_mod);
+    if (old_metadata.isValid()) {
+        emit hasOldMod(old_metadata.name, old_metadata.filename);
+        if (m_mod.slug.isEmpty())
+            m_mod.slug = old_metadata.slug;
+    }
 
-    emitSucceeded();
+    auto pw_mod = Metadata::create(m_index_dir, m_mod, m_mod_version);
+    if (pw_mod.isValid()) {
+        Metadata::update(m_index_dir, pw_mod);
+        emitSucceeded();
+    } else {
+        qCritical() << "Tried to update an invalid mod!";
+        emitFailed(tr("Invalid metadata"));
+    }
 }
 
 auto LocalModUpdateTask::abort() -> bool

launcher/minecraft/mod/tasks/LocalModUpdateTask.h

@@ -37,6 +37,9 @@ class LocalModUpdateTask : public Task {
     //! Entry point for tasks.
     void executeTask() override;
 
+   signals:
+    void hasOldMod(QString name, QString filename);
+
    private:
     QDir m_index_dir;
     ModPlatform::IndexedPack& m_mod;

launcher/minecraft/mod/tasks/ModFolderLoadTask.cpp

@@ -36,7 +36,6 @@
 
 #include "ModFolderLoadTask.h"
 
-#include "Application.h"
 #include "minecraft/mod/MetadataHandler.h"
 
 ModFolderLoadTask::ModFolderLoadTask(QDir& mods_dir, QDir& index_dir, bool is_indexed) 
@@ -53,33 +52,33 @@ void ModFolderLoadTask::run()
     // Read JAR files that don't have metadata
     m_mods_dir.refresh();
     for (auto entry : m_mods_dir.entryInfoList()) {
-        Mod mod(entry);
+        Mod::Ptr mod(new Mod(entry));
 
-        if (mod.enabled()) {
+        if (mod->enabled()) {
-            if (m_result->mods.contains(mod.internal_id())) {
+            if (m_result->mods.contains(mod->internal_id())) {
-                m_result->mods[mod.internal_id()].setStatus(ModStatus::Installed);
+                m_result->mods[mod->internal_id()]->setStatus(ModStatus::Installed);
             }
             else {
-                m_result->mods[mod.internal_id()] = mod;
+                m_result->mods[mod->internal_id()] = mod;
-                m_result->mods[mod.internal_id()].setStatus(ModStatus::NoMetadata);
+                m_result->mods[mod->internal_id()]->setStatus(ModStatus::NoMetadata);
             }
         }
         else { 
-            QString chopped_id = mod.internal_id().chopped(9);
+            QString chopped_id = mod->internal_id().chopped(9);
             if (m_result->mods.contains(chopped_id)) {
-                m_result->mods[mod.internal_id()] = mod;
+                m_result->mods[mod->internal_id()] = mod;
 
-                auto metadata = m_result->mods[chopped_id].metadata();
+                auto metadata = m_result->mods[chopped_id]->metadata();
                 if (metadata) {
-                    mod.setMetadata(new Metadata::ModStruct(*metadata));
+                    mod->setMetadata(*metadata);
 
-                    m_result->mods[mod.internal_id()].setStatus(ModStatus::Installed);
+                    m_result->mods[mod->internal_id()]->setStatus(ModStatus::Installed);
                     m_result->mods.remove(chopped_id);
                 }
             }
             else {
-                m_result->mods[mod.internal_id()] = mod;
+                m_result->mods[mod->internal_id()] = mod;
-                m_result->mods[mod.internal_id()].setStatus(ModStatus::NoMetadata);
+                m_result->mods[mod->internal_id()]->setStatus(ModStatus::NoMetadata);
             }
         }
     }
@@ -97,8 +96,8 @@ void ModFolderLoadTask::getFromMetadata()
             return;
         }
 
-        Mod mod(m_mods_dir, metadata);
+        auto* mod = new Mod(m_mods_dir, metadata);
-        mod.setStatus(ModStatus::NotInstalled);
+        mod->setStatus(ModStatus::NotInstalled);
-        m_result->mods[mod.internal_id()] = mod;
+        m_result->mods[mod->internal_id()] = mod;
     }
 }

launcher/minecraft/mod/tasks/ModFolderLoadTask.h

@@ -48,7 +48,7 @@ class ModFolderLoadTask : public QObject, public QRunnable
     Q_OBJECT
 public:
     struct Result {
-        QMap<QString, Mod> mods;
+        QMap<QString, Mod::Ptr> mods;
     };
     using ResultPtr = std::shared_ptr<Result>;
     ResultPtr result() const {

launcher/modplatform/CheckUpdateTask.h

@@ -0,0 +1,51 @@
+#pragma once
+
+#include "minecraft/mod/Mod.h"
+#include "modplatform/ModAPI.h"
+#include "modplatform/ModIndex.h"
+#include "tasks/Task.h"
+
+class ModDownloadTask;
+class ModFolderModel;
+
+class CheckUpdateTask : public Task {
+    Q_OBJECT
+
+   public:
+    CheckUpdateTask(QList<Mod*>& mods, std::list<Version>& mcVersions, ModAPI::ModLoaderTypes loaders, std::shared_ptr<ModFolderModel> mods_folder)
+        : Task(nullptr), m_mods(mods), m_game_versions(mcVersions), m_loaders(loaders), m_mods_folder(mods_folder) {};
+
+    struct UpdatableMod {
+        QString name;
+        QString old_hash;
+        QString old_version;
+        QString new_version;
+        QString changelog;
+        ModPlatform::Provider provider;
+        ModDownloadTask* download;
+
+       public:
+        UpdatableMod(QString name, QString old_h, QString old_v, QString new_v, QString changelog, ModPlatform::Provider p, ModDownloadTask* t)
+            : name(name), old_hash(old_h), old_version(old_v), new_version(new_v), changelog(changelog), provider(p), download(t)
+        {}
+    };
+
+    auto getUpdatable() -> std::vector<UpdatableMod>&& { return std::move(m_updatable); }
+
+   public slots:
+    bool abort() override = 0;
+
+   protected slots:
+    void executeTask() override = 0;
+
+   signals:
+    void checkFailed(Mod* failed, QString reason, QUrl recover_url = {});
+
+   protected:
+    QList<Mod*>& m_mods;
+    std::list<Version>& m_game_versions;
+    ModAPI::ModLoaderTypes m_loaders;
+    std::shared_ptr<ModFolderModel> m_mods_folder;
+
+    std::vector<UpdatableMod> m_updatable;
+};

launcher/modplatform/EnsureMetadataTask.cpp

@@ -0,0 +1,534 @@
+#include "EnsureMetadataTask.h"
+
+#include <MurmurHash2.h>
+#include <QDebug>
+
+#include "FileSystem.h"
+#include "Json.h"
+#include "minecraft/mod/Mod.h"
+#include "minecraft/mod/tasks/LocalModUpdateTask.h"
+#include "modplatform/flame/FlameAPI.h"
+#include "modplatform/flame/FlameModIndex.h"
+#include "modplatform/modrinth/ModrinthAPI.h"
+#include "modplatform/modrinth/ModrinthPackIndex.h"
+#include "net/NetJob.h"
+#include "tasks/MultipleOptionsTask.h"
+
+static ModPlatform::ProviderCapabilities ProviderCaps;
+
+static ModrinthAPI modrinth_api;
+static FlameAPI flame_api;
+
+EnsureMetadataTask::EnsureMetadataTask(Mod* mod, QDir dir, ModPlatform::Provider prov) : Task(nullptr), m_index_dir(dir), m_provider(prov)
+{
+    auto hash = getHash(mod);
+    if (hash.isEmpty())
+        emitFail(mod);
+    else
+        m_mods.insert(hash, mod);
+}
+
+EnsureMetadataTask::EnsureMetadataTask(QList<Mod*>& mods, QDir dir, ModPlatform::Provider prov)
+    : Task(nullptr), m_index_dir(dir), m_provider(prov)
+{
+    for (auto* mod : mods) {
+        if (!mod->valid()) {
+            emitFail(mod);
+            continue;
+        }
+
+        auto hash = getHash(mod);
+        if (hash.isEmpty()) {
+            emitFail(mod);
+            continue;
+        }
+
+        m_mods.insert(hash, mod);
+    }
+}
+
+QString EnsureMetadataTask::getHash(Mod* mod)
+{
+    /* Here we create a mapping hash -> mod, because we need that relationship to parse the API routes */
+    QByteArray jar_data;
+    try {
+        jar_data = FS::read(mod->fileinfo().absoluteFilePath());
+    } catch (FS::FileSystemException& e) {
+        qCritical() << QString("Failed to open / read JAR file of %1").arg(mod->name());
+        qCritical() << QString("Reason: ") << e.cause();
+
+        return {};
+    }
+
+    switch (m_provider) {
+        case ModPlatform::Provider::MODRINTH: {
+            auto hash_type = ProviderCaps.hashType(ModPlatform::Provider::MODRINTH).first();
+
+            return QString(ProviderCaps.hash(ModPlatform::Provider::MODRINTH, jar_data, hash_type).toHex());
+        }
+        case ModPlatform::Provider::FLAME: {
+            QByteArray jar_data_treated;
+            for (char c : jar_data) {
+                // CF-specific
+                if (!(c == 9 || c == 10 || c == 13 || c == 32))
+                    jar_data_treated.push_back(c);
+            }
+
+            return QString::number(MurmurHash2(jar_data_treated, jar_data_treated.length()));
+        }
+    }
+
+    return {};
+}
+
+bool EnsureMetadataTask::abort()
+{
+    // Prevent sending signals to a dead object
+    disconnect(this, 0, 0, 0);
+
+    if (m_current_task)
+        return m_current_task->abort();
+    return true;
+}
+
+void EnsureMetadataTask::executeTask()
+{
+    setStatus(tr("Checking if mods have metadata..."));
+
+    for (auto* mod : m_mods) {
+        if (!mod->valid()) {
+            qDebug() << "Mod" << mod->name() << "is invalid!";
+            emitFail(mod);
+            continue;
+        }
+
+        // They already have the right metadata :o
+        if (mod->status() != ModStatus::NoMetadata && mod->metadata() && mod->metadata()->provider == m_provider) {
+            qDebug() << "Mod" << mod->name() << "already has metadata!";
+            emitReady(mod);
+            continue;
+        }
+
+        // Folders don't have metadata
+        if (mod->type() == Mod::MOD_FOLDER) {
+            emitReady(mod);
+        }
+    }
+
+    NetJob::Ptr version_task;
+
+    switch (m_provider) {
+        case (ModPlatform::Provider::MODRINTH):
+            version_task = modrinthVersionsTask();
+            break;
+        case (ModPlatform::Provider::FLAME):
+            version_task = flameVersionsTask();
+            break;
+    }
+
+    auto invalidade_leftover = [this] {
+        QMutableHashIterator<QString, Mod*> mods_iter(m_mods);
+        while (mods_iter.hasNext()) {
+            auto mod = mods_iter.next();
+            emitFail(mod.value());
+        }
+
+        emitSucceeded();
+    };
+
+    connect(version_task.get(), &Task::finished, this, [this, invalidade_leftover] {
+        NetJob::Ptr project_task;
+
+        switch (m_provider) {
+            case (ModPlatform::Provider::MODRINTH):
+                project_task = modrinthProjectsTask();
+                break;
+            case (ModPlatform::Provider::FLAME):
+                project_task = flameProjectsTask();
+                break;
+        }
+
+        if (!project_task) {
+            invalidade_leftover();
+            return;
+        }
+
+        connect(project_task.get(), &Task::finished, this, [=] {
+            invalidade_leftover();
+            project_task->deleteLater();
+            m_current_task = nullptr;
+        });
+
+        m_current_task = project_task.get();
+        project_task->start();
+    });
+
+    connect(version_task.get(), &Task::finished, [=] {
+        version_task->deleteLater();
+        m_current_task = nullptr;
+    });
+
+    if (m_mods.size() > 1)
+        setStatus(tr("Requesting metadata information from %1...").arg(ProviderCaps.readableName(m_provider)));
+    else if (!m_mods.empty())
+        setStatus(tr("Requesting metadata information from %1 for '%2'...")
+                      .arg(ProviderCaps.readableName(m_provider), m_mods.begin().value()->name()));
+
+    m_current_task = version_task.get();
+    version_task->start();
+}
+
+void EnsureMetadataTask::emitReady(Mod* m)
+{
+    qDebug() << QString("Generated metadata for %1").arg(m->name());
+    emit metadataReady(m);
+
+    m_mods.remove(getHash(m));
+}
+
+void EnsureMetadataTask::emitFail(Mod* m)
+{
+    qDebug() << QString("Failed to generate metadata for %1").arg(m->name());
+    emit metadataFailed(m);
+
+    m_mods.remove(getHash(m));
+}
+
+// Modrinth
+
+NetJob::Ptr EnsureMetadataTask::modrinthVersionsTask()
+{
+    auto hash_type = ProviderCaps.hashType(ModPlatform::Provider::MODRINTH).first();
+
+    auto* response = new QByteArray();
+    auto ver_task = modrinth_api.currentVersions(m_mods.keys(), hash_type, response);
+
+    // Prevents unfortunate timings when aborting the task
+    if (!ver_task)
+        return {};
+
+    connect(ver_task.get(), &NetJob::succeeded, this, [this, response] {
+        QJsonParseError parse_error{};
+        QJsonDocument doc = QJsonDocument::fromJson(*response, &parse_error);
+        if (parse_error.error != QJsonParseError::NoError) {
+            qWarning() << "Error while parsing JSON response from Modrinth::CurrentVersions at " << parse_error.offset
+                       << " reason: " << parse_error.errorString();
+            qWarning() << *response;
+
+            failed(parse_error.errorString());
+            return;
+        }
+
+        try {
+            auto entries = Json::requireObject(doc);
+            for (auto& hash : m_mods.keys()) {
+                auto mod = m_mods.find(hash).value();
+                try {
+                    auto entry = Json::requireObject(entries, hash);
+
+                    setStatus(tr("Parsing API response from Modrinth for '%1'...").arg(mod->name()));
+                    qDebug() << "Getting version for" << mod->name() << "from Modrinth";
+
+                    m_temp_versions.insert(hash, Modrinth::loadIndexedPackVersion(entry));
+                } catch (Json::JsonException& e) {
+                    qDebug() << e.cause();
+                    qDebug() << entries;
+
+                    emitFail(mod);
+                }
+            }
+        } catch (Json::JsonException& e) {
+            qDebug() << e.cause();
+            qDebug() << doc;
+        }
+    });
+
+    return ver_task;
+}
+
+NetJob::Ptr EnsureMetadataTask::modrinthProjectsTask()
+{
+    QHash<QString, QString> addonIds;
+    for (auto const& data : m_temp_versions)
+        addonIds.insert(data.addonId.toString(), data.hash);
+
+    auto response = new QByteArray();
+    NetJob::Ptr proj_task;
+
+    if (addonIds.isEmpty()) {
+        qWarning() << "No addonId found!";
+    } else if (addonIds.size() == 1) {
+        proj_task = modrinth_api.getProject(*addonIds.keyBegin(), response);
+    } else {
+        proj_task = modrinth_api.getProjects(addonIds.keys(), response);
+    }
+
+    // Prevents unfortunate timings when aborting the task
+    if (!proj_task)
+        return {};
+
+    connect(proj_task.get(), &NetJob::succeeded, this, [this, response, addonIds] {
+        QJsonParseError parse_error{};
+        auto doc = QJsonDocument::fromJson(*response, &parse_error);
+        if (parse_error.error != QJsonParseError::NoError) {
+            qWarning() << "Error while parsing JSON response from Modrinth projects task at " << parse_error.offset
+                       << " reason: " << parse_error.errorString();
+            qWarning() << *response;
+            return;
+        }
+
+        try {
+            QJsonArray entries;
+            if (addonIds.size() == 1)
+                entries = { doc.object() };
+            else
+                entries = Json::requireArray(doc);
+
+            for (auto entry : entries) {
+                auto entry_obj = Json::requireObject(entry);
+
+                ModPlatform::IndexedPack pack;
+                Modrinth::loadIndexedPack(pack, entry_obj);
+
+                auto hash = addonIds.find(pack.addonId.toString()).value();
+
+                auto mod_iter = m_mods.find(hash);
+                if (mod_iter == m_mods.end()) {
+                    qWarning() << "Invalid project id from the API response.";
+                    continue;
+                }
+
+                auto* mod = mod_iter.value();
+
+                try {
+                    setStatus(tr("Parsing API response from Modrinth for '%1'...").arg(mod->name()));
+
+                    modrinthCallback(pack, m_temp_versions.find(hash).value(), mod);
+                } catch (Json::JsonException& e) {
+                    qDebug() << e.cause();
+                    qDebug() << entries;
+
+                    emitFail(mod);
+                }
+            }
+        } catch (Json::JsonException& e) {
+            qDebug() << e.cause();
+            qDebug() << doc;
+        }
+    });
+
+    return proj_task;
+}
+
+// Flame
+NetJob::Ptr EnsureMetadataTask::flameVersionsTask()
+{
+    auto* response = new QByteArray();
+
+    QList<uint> fingerprints;
+    for (auto& murmur : m_mods.keys()) {
+        fingerprints.push_back(murmur.toUInt());
+    }
+
+    auto ver_task = flame_api.matchFingerprints(fingerprints, response);
+
+    connect(ver_task.get(), &Task::succeeded, this, [this, response] {
+        QJsonParseError parse_error{};
+        QJsonDocument doc = QJsonDocument::fromJson(*response, &parse_error);
+        if (parse_error.error != QJsonParseError::NoError) {
+            qWarning() << "Error while parsing JSON response from Modrinth::CurrentVersions at " << parse_error.offset
+                       << " reason: " << parse_error.errorString();
+            qWarning() << *response;
+
+            failed(parse_error.errorString());
+            return;
+        }
+
+        try {
+            auto doc_obj = Json::requireObject(doc);
+            auto data_obj = Json::requireObject(doc_obj, "data");
+            auto data_arr = Json::requireArray(data_obj, "exactMatches");
+
+            if (data_arr.isEmpty()) {
+                qWarning() << "No matches found for fingerprint search!";
+
+                return;
+            }
+
+            for (auto match : data_arr) {
+                auto match_obj = Json::ensureObject(match, {});
+                auto file_obj = Json::ensureObject(match_obj, "file", {});
+
+                if (match_obj.isEmpty() || file_obj.isEmpty()) {
+                    qWarning() << "Fingerprint match is empty!";
+
+                    return;
+                }
+
+                auto fingerprint = QString::number(Json::ensureVariant(file_obj, "fileFingerprint").toUInt());
+                auto mod = m_mods.find(fingerprint);
+                if (mod == m_mods.end()) {
+                    qWarning() << "Invalid fingerprint from the API response.";
+                    continue;
+                }
+
+                setStatus(tr("Parsing API response from CurseForge for '%1'...").arg((*mod)->name()));
+
+                m_temp_versions.insert(fingerprint, FlameMod::loadIndexedPackVersion(file_obj));
+            }
+
+        } catch (Json::JsonException& e) {
+            qDebug() << e.cause();
+            qDebug() << doc;
+        }
+    });
+
+    return ver_task;
+}
+
+NetJob::Ptr EnsureMetadataTask::flameProjectsTask()
+{
+    QHash<QString, QString> addonIds;
+    for (auto const& hash : m_mods.keys()) {
+        if (m_temp_versions.contains(hash)) {
+            auto const& data = m_temp_versions.find(hash).value();
+
+            auto id_str = data.addonId.toString();
+            if (!id_str.isEmpty())
+                addonIds.insert(data.addonId.toString(), hash);
+        }
+    }
+
+    auto response = new QByteArray();
+    NetJob::Ptr proj_task;
+
+    if (addonIds.isEmpty()) {
+        qWarning() << "No addonId found!";
+    } else if (addonIds.size() == 1) {
+        proj_task = flame_api.getProject(*addonIds.keyBegin(), response);
+    } else {
+        proj_task = flame_api.getProjects(addonIds.keys(), response);
+    }
+
+    // Prevents unfortunate timings when aborting the task
+    if (!proj_task)
+        return {};
+
+    connect(proj_task.get(), &NetJob::succeeded, this, [this, response, addonIds] {
+        QJsonParseError parse_error{};
+        auto doc = QJsonDocument::fromJson(*response, &parse_error);
+        if (parse_error.error != QJsonParseError::NoError) {
+            qWarning() << "Error while parsing JSON response from Modrinth projects task at " << parse_error.offset
+                       << " reason: " << parse_error.errorString();
+            qWarning() << *response;
+            return;
+        }
+
+        try {
+            QJsonArray entries;
+            if (addonIds.size() == 1)
+                entries = { Json::requireObject(Json::requireObject(doc), "data") };
+            else
+                entries = Json::requireArray(Json::requireObject(doc), "data");
+
+            for (auto entry : entries) {
+                auto entry_obj = Json::requireObject(entry);
+
+                auto id = QString::number(Json::requireInteger(entry_obj, "id"));
+                auto hash = addonIds.find(id).value();
+                auto mod = m_mods.find(hash).value();
+
+                try {
+                    setStatus(tr("Parsing API response from CurseForge for '%1'...").arg(mod->name()));
+
+                    ModPlatform::IndexedPack pack;
+                    FlameMod::loadIndexedPack(pack, entry_obj);
+
+                    flameCallback(pack, m_temp_versions.find(hash).value(), mod);
+                } catch (Json::JsonException& e) {
+                    qDebug() << e.cause();
+                    qDebug() << entries;
+
+                    emitFail(mod);
+                }
+            }
+        } catch (Json::JsonException& e) {
+            qDebug() << e.cause();
+            qDebug() << doc;
+        }
+    });
+
+    return proj_task;
+}
+
+void EnsureMetadataTask::modrinthCallback(ModPlatform::IndexedPack& pack, ModPlatform::IndexedVersion& ver, Mod* mod)
+{
+    // Prevent file name mismatch
+    ver.fileName = mod->fileinfo().fileName();
+    if (ver.fileName.endsWith(".disabled"))
+        ver.fileName.chop(9);
+
+    QDir tmp_index_dir(m_index_dir);
+
+    {
+        LocalModUpdateTask update_metadata(m_index_dir, pack, ver);
+        QEventLoop loop;
+
+        QObject::connect(&update_metadata, &Task::finished, &loop, &QEventLoop::quit);
+
+        update_metadata.start();
+
+        if (!update_metadata.isFinished())
+            loop.exec();
+    }
+
+    auto metadata = Metadata::get(tmp_index_dir, pack.slug);
+    if (!metadata.isValid()) {
+        qCritical() << "Failed to generate metadata at last step!";
+        emitFail(mod);
+        return;
+    }
+
+    mod->setMetadata(metadata);
+
+    emitReady(mod);
+}
+
+void EnsureMetadataTask::flameCallback(ModPlatform::IndexedPack& pack, ModPlatform::IndexedVersion& ver, Mod* mod)
+{
+    try {
+        // Prevent file name mismatch
+        ver.fileName = mod->fileinfo().fileName();
+        if (ver.fileName.endsWith(".disabled"))
+            ver.fileName.chop(9);
+
+        QDir tmp_index_dir(m_index_dir);
+
+        {
+            LocalModUpdateTask update_metadata(m_index_dir, pack, ver);
+            QEventLoop loop;
+
+            QObject::connect(&update_metadata, &Task::finished, &loop, &QEventLoop::quit);
+
+            update_metadata.start();
+
+            if (!update_metadata.isFinished())
+                loop.exec();
+        }
+
+        auto metadata = Metadata::get(tmp_index_dir, pack.slug);
+        if (!metadata.isValid()) {
+            qCritical() << "Failed to generate metadata at last step!";
+            emitFail(mod);
+            return;
+        }
+
+        mod->setMetadata(metadata);
+
+        emitReady(mod);
+    } catch (Json::JsonException& e) {
+        qDebug() << e.cause();
+
+        emitFail(mod);
+    }
+}

launcher/modplatform/EnsureMetadataTask.h

@@ -0,0 +1,54 @@
+#pragma once
+
+#include "ModIndex.h"
+#include "tasks/SequentialTask.h"
+#include "net/NetJob.h"
+
+class Mod;
+class QDir;
+class MultipleOptionsTask;
+
+class EnsureMetadataTask : public Task {
+    Q_OBJECT
+
+   public:
+    EnsureMetadataTask(Mod*, QDir, ModPlatform::Provider = ModPlatform::Provider::MODRINTH);
+    EnsureMetadataTask(QList<Mod*>&, QDir, ModPlatform::Provider = ModPlatform::Provider::MODRINTH);
+
+    ~EnsureMetadataTask() = default;
+
+   public slots:
+    bool abort() override;
+   protected slots:
+    void executeTask() override;
+
+   private:
+    // FIXME: Move to their own namespace
+    auto modrinthVersionsTask() -> NetJob::Ptr;
+    auto modrinthProjectsTask() -> NetJob::Ptr;
+
+    auto flameVersionsTask() -> NetJob::Ptr;
+    auto flameProjectsTask() -> NetJob::Ptr;
+
+    // Helpers
+    void emitReady(Mod*);
+    void emitFail(Mod*);
+
+    auto getHash(Mod*) -> QString;
+
+   private slots:
+    void modrinthCallback(ModPlatform::IndexedPack& pack, ModPlatform::IndexedVersion& ver, Mod*);
+    void flameCallback(ModPlatform::IndexedPack& pack, ModPlatform::IndexedVersion& ver, Mod*);
+
+   signals:
+    void metadataReady(Mod*);
+    void metadataFailed(Mod*);
+
+   private:
+    QHash<QString, Mod*> m_mods;
+    QDir m_index_dir;
+    ModPlatform::Provider m_provider;
+
+    QHash<QString, ModPlatform::IndexedVersion> m_temp_versions;
+    NetJob* m_current_task;
+};

launcher/modplatform/ModAPI.h

@@ -40,6 +40,7 @@
 #include <list>
 
 #include "Version.h"
+#include "net/NetJob.h"
 
 namespace ModPlatform {
 class ListModel;
@@ -74,6 +75,9 @@ class ModAPI {
     virtual void searchMods(CallerType* caller, SearchArgs&& args) const = 0;
     virtual void getModInfo(CallerType* caller, ModPlatform::IndexedPack& pack) = 0;
 
+    virtual auto getProject(QString addonId, QByteArray* response) const -> NetJob* = 0;
+    virtual auto getProjects(QStringList addonIds, QByteArray* response) const -> NetJob* = 0;
+
 
     struct VersionSearchArgs {
         QString addonId;

launcher/modplatform/ModIndex.h

@@ -54,13 +54,16 @@ struct IndexedVersion {
     QVariant addonId;
     QVariant fileId;
     QString version;
-    QVector<QString> mcVersion;
+    QString version_number = {};
+    QStringList mcVersion;
     QString downloadUrl;
     QString date;
     QString fileName;
-    QVector<QString> loaders = {};
+    QStringList loaders = {};
     QString hash_type;
     QString hash;
+    bool is_preferred = true;
+    QString changelog;
 };
 
 struct ExtraPackData {
@@ -76,6 +79,7 @@ struct IndexedPack {
     QVariant addonId;
     Provider provider;
     QString name;
+    QString slug;
     QString description;
     QList<ModpackAuthor> authors;
     QString logoName;

launcher/modplatform/flame/FlameAPI.cpp

@@ -0,0 +1,148 @@
+#include "FlameAPI.h"
+#include "FlameModIndex.h"
+
+#include "Application.h"
+#include "BuildConfig.h"
+#include "Json.h"
+
+#include "net/Upload.h"
+
+auto FlameAPI::matchFingerprints(const QList<uint>& fingerprints, QByteArray* response) -> NetJob::Ptr
+{
+    auto* netJob = new NetJob(QString("Flame::MatchFingerprints"), APPLICATION->network());
+
+    QJsonObject body_obj;
+    QJsonArray fingerprints_arr;
+    for (auto& fp : fingerprints) {
+        fingerprints_arr.append(QString("%1").arg(fp));
+    }
+
+    body_obj["fingerprints"] = fingerprints_arr;
+
+    QJsonDocument body(body_obj);
+    auto body_raw = body.toJson();
+
+    netJob->addNetAction(Net::Upload::makeByteArray(QString("https://api.curseforge.com/v1/fingerprints"), response, body_raw));
+
+    QObject::connect(netJob, &NetJob::finished, [response] { delete response; });
+
+    return netJob;
+}
+
+auto FlameAPI::getModFileChangelog(int modId, int fileId) -> QString
+{
+    QEventLoop lock;
+    QString changelog;
+
+    auto* netJob = new NetJob(QString("Flame::FileChangelog"), APPLICATION->network());
+    auto* response = new QByteArray();
+    netJob->addNetAction(Net::Download::makeByteArray(
+        QString("https://api.curseforge.com/v1/mods/%1/files/%2/changelog")
+            .arg(QString::fromStdString(std::to_string(modId)), QString::fromStdString(std::to_string(fileId))),
+        response));
+
+    QObject::connect(netJob, &NetJob::succeeded, [netJob, response, &changelog] {
+        QJsonParseError parse_error{};
+        QJsonDocument doc = QJsonDocument::fromJson(*response, &parse_error);
+        if (parse_error.error != QJsonParseError::NoError) {
+            qWarning() << "Error while parsing JSON response from Flame::FileChangelog at " << parse_error.offset
+                       << " reason: " << parse_error.errorString();
+            qWarning() << *response;
+
+            netJob->failed(parse_error.errorString());
+            return;
+        }
+
+        changelog = Json::ensureString(doc.object(), "data");
+    });
+
+    QObject::connect(netJob, &NetJob::finished, [response, &lock] {
+        delete response;
+        lock.quit();
+    });
+
+    netJob->start();
+    lock.exec();
+
+    return changelog;
+}
+
+auto FlameAPI::getLatestVersion(VersionSearchArgs&& args) -> ModPlatform::IndexedVersion
+{
+    QEventLoop loop;
+
+    auto netJob = new NetJob(QString("Flame::GetLatestVersion(%1)").arg(args.addonId), APPLICATION->network());
+    auto response = new QByteArray();
+    ModPlatform::IndexedVersion ver;
+
+    netJob->addNetAction(Net::Download::makeByteArray(getVersionsURL(args), response));
+
+    QObject::connect(netJob, &NetJob::succeeded, [response, args, &ver] {
+        QJsonParseError parse_error{};
+        QJsonDocument doc = QJsonDocument::fromJson(*response, &parse_error);
+        if (parse_error.error != QJsonParseError::NoError) {
+            qWarning() << "Error while parsing JSON response from latest mod version at " << parse_error.offset
+                       << " reason: " << parse_error.errorString();
+            qWarning() << *response;
+            return;
+        }
+
+        try {
+            auto obj = Json::requireObject(doc);
+            auto arr = Json::requireArray(obj, "data");
+
+            QJsonObject latest_file_obj;
+            ModPlatform::IndexedVersion ver_tmp;
+
+            for (auto file : arr) {
+                auto file_obj = Json::requireObject(file);
+                auto file_tmp = FlameMod::loadIndexedPackVersion(file_obj);
+                if(file_tmp.date > ver_tmp.date) {
+                    ver_tmp = file_tmp;
+                    latest_file_obj = file_obj;
+                }
+            }
+
+            ver = FlameMod::loadIndexedPackVersion(latest_file_obj);
+        } catch (Json::JsonException& e) {
+            qCritical() << "Failed to parse response from a version request.";
+            qCritical() << e.what();
+            qDebug() << doc;
+        }
+    });
+
+    QObject::connect(netJob, &NetJob::finished, [response, netJob, &loop] {
+        netJob->deleteLater();
+        delete response;
+        loop.quit();
+    });
+
+    netJob->start();
+
+    loop.exec();
+
+    return ver;
+}
+
+auto FlameAPI::getProjects(QStringList addonIds, QByteArray* response) const -> NetJob*
+{
+    auto* netJob = new NetJob(QString("Flame::GetProjects"), APPLICATION->network());
+
+    QJsonObject body_obj;
+    QJsonArray addons_arr;
+    for (auto& addonId : addonIds) {
+        addons_arr.append(addonId);
+    }
+
+    body_obj["modIds"] = addons_arr;
+
+    QJsonDocument body(body_obj);
+    auto body_raw = body.toJson();
+
+    netJob->addNetAction(Net::Upload::makeByteArray(QString("https://api.curseforge.com/v1/mods"), response, body_raw));
+
+    QObject::connect(netJob, &NetJob::finished, [response, netJob] { delete response; netJob->deleteLater(); });
+    QObject::connect(netJob, &NetJob::failed, [body_raw] { qDebug() << body_raw; });
+
+    return netJob;
+}

launcher/modplatform/flame/FlameAPI.h

@@ -4,6 +4,14 @@
 #include "modplatform/helpers/NetworkModAPI.h"
 
 class FlameAPI : public NetworkModAPI {
+   public:
+    auto matchFingerprints(const QList<uint>& fingerprints, QByteArray* response) -> NetJob::Ptr;
+    auto getModFileChangelog(int modId, int fileId) -> QString;
+
+    auto getLatestVersion(VersionSearchArgs&& args) -> ModPlatform::IndexedVersion;
+
+    auto getProjects(QStringList addonIds, QByteArray* response) const -> NetJob* override;
+
    private:
     inline auto getSortFieldInt(QString sortString) const -> int
     {

launcher/modplatform/flame/FlameCheckUpdate.cpp

@@ -0,0 +1,179 @@
+#include "FlameCheckUpdate.h"
+#include "FlameAPI.h"
+#include "FlameModIndex.h"
+
+#include <MurmurHash2.h>
+
+#include "FileSystem.h"
+#include "Json.h"
+
+#include "ModDownloadTask.h"
+
+static FlameAPI api;
+
+bool FlameCheckUpdate::abort()
+{
+    m_was_aborted = true;
+    if (m_net_job)
+        return m_net_job->abort();
+    return true;
+}
+
+ModPlatform::IndexedPack getProjectInfo(ModPlatform::IndexedVersion& ver_info)
+{
+    ModPlatform::IndexedPack pack;
+
+    QEventLoop loop;
+
+    auto get_project_job = new NetJob("Flame::GetProjectJob", APPLICATION->network());
+
+    auto response = new QByteArray();
+    auto url = QString("https://api.curseforge.com/v1/mods/%1").arg(ver_info.addonId.toString());
+    auto dl = Net::Download::makeByteArray(url, response);
+    get_project_job->addNetAction(dl);
+
+    QObject::connect(get_project_job, &NetJob::succeeded, [response, &pack]() {
+        QJsonParseError parse_error{};
+        QJsonDocument doc = QJsonDocument::fromJson(*response, &parse_error);
+        if (parse_error.error != QJsonParseError::NoError) {
+            qWarning() << "Error while parsing JSON response from FlameCheckUpdate at " << parse_error.offset
+                       << " reason: " << parse_error.errorString();
+            qWarning() << *response;
+            return;
+        }
+
+        try {
+            auto doc_obj = Json::requireObject(doc);
+            auto data_obj = Json::requireObject(doc_obj, "data");
+            FlameMod::loadIndexedPack(pack, data_obj);
+        } catch (Json::JsonException& e) {
+            qWarning() << e.cause();
+            qDebug() << doc;
+        }
+    });
+
+    QObject::connect(get_project_job, &NetJob::finished, [&loop, get_project_job] {
+        get_project_job->deleteLater();
+        loop.quit();
+    });
+
+    get_project_job->start();
+    loop.exec();
+
+    return pack;
+}
+
+ModPlatform::IndexedVersion getFileInfo(int addonId, int fileId)
+{
+    ModPlatform::IndexedVersion ver;
+
+    QEventLoop loop;
+
+    auto get_file_info_job = new NetJob("Flame::GetFileInfoJob", APPLICATION->network());
+
+    auto response = new QByteArray();
+    auto url = QString("https://api.curseforge.com/v1/mods/%1/files/%2").arg(QString::number(addonId), QString::number(fileId));
+    auto dl = Net::Download::makeByteArray(url, response);
+    get_file_info_job->addNetAction(dl);
+
+    QObject::connect(get_file_info_job, &NetJob::succeeded, [response, &ver]() {
+        QJsonParseError parse_error{};
+        QJsonDocument doc = QJsonDocument::fromJson(*response, &parse_error);
+        if (parse_error.error != QJsonParseError::NoError) {
+            qWarning() << "Error while parsing JSON response from FlameCheckUpdate at " << parse_error.offset
+                       << " reason: " << parse_error.errorString();
+            qWarning() << *response;
+            return;
+        }
+
+        try {
+            auto doc_obj = Json::requireObject(doc);
+            auto data_obj = Json::requireObject(doc_obj, "data");
+            ver = FlameMod::loadIndexedPackVersion(data_obj);
+        } catch (Json::JsonException& e) {
+            qWarning() << e.cause();
+            qDebug() << doc;
+        }
+    });
+
+    QObject::connect(get_file_info_job, &NetJob::finished, [&loop, get_file_info_job] {
+        get_file_info_job->deleteLater();
+        loop.quit();
+    });
+
+    get_file_info_job->start();
+    loop.exec();
+
+    return ver;
+}
+
+/* Check for update:
+ * - Get latest version available
+ * - Compare hash of the latest version with the current hash
+ * - If equal, no updates, else, there's updates, so add to the list
+ * */
+void FlameCheckUpdate::executeTask()
+{
+    setStatus(tr("Preparing mods for CurseForge..."));
+
+    int i = 0;
+    for (auto* mod : m_mods) {
+        if (!mod->enabled()) {
+            emit checkFailed(mod, tr("Disabled mods won't be updated, to prevent mod duplication issues!"));
+            continue;
+        }
+
+        setStatus(tr("Getting API response from CurseForge for '%1'").arg(mod->name()));
+        setProgress(i++, m_mods.size());
+
+        auto latest_ver = api.getLatestVersion({ mod->metadata()->project_id.toString(), m_game_versions, m_loaders });
+
+        // Check if we were aborted while getting the latest version
+        if (m_was_aborted) {
+            aborted();
+            return;
+        }
+
+        setStatus(tr("Parsing the API response from CurseForge for '%1'...").arg(mod->name()));
+
+        if (!latest_ver.addonId.isValid()) {
+            emit checkFailed(mod, tr("No valid version found for this mod. It's probably unavailable for the current game "
+                                     "version / mod loader."));
+            continue;
+        }
+
+        if (latest_ver.downloadUrl.isEmpty() && latest_ver.fileId != mod->metadata()->file_id) {
+            auto pack = getProjectInfo(latest_ver);
+            auto recover_url = QString("%1/download/%2").arg(pack.websiteUrl, latest_ver.fileId.toString());
+            emit checkFailed(mod, tr("Mod has a new update available, but is opted-out on CurseForge"), recover_url);
+
+            continue;
+        }
+
+        if (!latest_ver.hash.isEmpty() && (mod->metadata()->hash != latest_ver.hash || mod->status() == ModStatus::NotInstalled)) {
+            // Fake pack with the necessary info to pass to the download task :)
+            ModPlatform::IndexedPack pack;
+            pack.name = mod->name();
+            pack.slug = mod->metadata()->slug;
+            pack.addonId = mod->metadata()->project_id;
+            pack.websiteUrl = mod->homeurl();
+            for (auto& author : mod->authors())
+                pack.authors.append({ author });
+            pack.description = mod->description();
+            pack.provider = ModPlatform::Provider::FLAME;
+
+            auto old_version = mod->version();
+            if (old_version.isEmpty() && mod->status() != ModStatus::NotInstalled) {
+                auto current_ver = getFileInfo(latest_ver.addonId.toInt(), mod->metadata()->file_id.toInt());
+                old_version = current_ver.version;
+            }
+
+            auto download_task = new ModDownloadTask(pack, latest_ver, m_mods_folder);
+            m_updatable.emplace_back(pack.name, mod->metadata()->hash, old_version, latest_ver.version,
+                                     api.getModFileChangelog(latest_ver.addonId.toInt(), latest_ver.fileId.toInt()),
+                                     ModPlatform::Provider::FLAME, download_task);
+        }
+    }
+
+    emitSucceeded();
+}

launcher/modplatform/flame/FlameCheckUpdate.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include "Application.h"
+#include "modplatform/CheckUpdateTask.h"
+#include "net/NetJob.h"
+
+class FlameCheckUpdate : public CheckUpdateTask {
+    Q_OBJECT
+
+   public:
+    FlameCheckUpdate(QList<Mod*>& mods, std::list<Version>& mcVersions, ModAPI::ModLoaderTypes loaders, std::shared_ptr<ModFolderModel> mods_folder)
+        : CheckUpdateTask(mods, mcVersions, loaders, mods_folder)
+    {}
+
+   public slots:
+    bool abort() override;
+
+   protected slots:
+    void executeTask() override;
+
+   private:
+    NetJob* m_net_job = nullptr;
+
+    bool m_was_aborted = false;
+};

launcher/modplatform/flame/FlameModIndex.cpp

@@ -7,20 +7,22 @@
 #include "net/NetJob.h"
 
 static ModPlatform::ProviderCapabilities ProviderCaps;
+static FlameAPI api;
 
 void FlameMod::loadIndexedPack(ModPlatform::IndexedPack& pack, QJsonObject& obj)
 {
     pack.addonId = Json::requireInteger(obj, "id");
     pack.provider = ModPlatform::Provider::FLAME;
     pack.name = Json::requireString(obj, "name");
+    pack.slug = Json::requireString(obj, "slug");
     pack.websiteUrl = Json::ensureString(Json::ensureObject(obj, "links"), "websiteUrl", "");
     pack.description = Json::ensureString(obj, "summary", "");
 
-    QJsonObject logo = Json::requireObject(obj, "logo");
+    QJsonObject logo = Json::ensureObject(obj, "logo");
-    pack.logoName = Json::requireString(logo, "title");
+    pack.logoName = Json::ensureString(logo, "title");
-    pack.logoUrl = Json::requireString(logo, "thumbnailUrl");
+    pack.logoUrl = Json::ensureString(logo, "thumbnailUrl");
 
-    auto authors = Json::requireArray(obj, "authors");
+    auto authors = Json::ensureArray(obj, "authors");
     for (auto authorIter : authors) {
         auto author = Json::requireObject(authorIter);
         ModPlatform::ModpackAuthor packAuthor;
@@ -91,7 +93,7 @@ void FlameMod::loadIndexedPackVersions(ModPlatform::IndexedPack& pack,
     pack.versionsLoaded = true;
 }
 
-auto FlameMod::loadIndexedPackVersion(QJsonObject& obj) -> ModPlatform::IndexedVersion
+auto FlameMod::loadIndexedPackVersion(QJsonObject& obj, bool load_changelog) -> ModPlatform::IndexedVersion
 {
     auto versionArray = Json::requireArray(obj, "gameVersions");
     if (versionArray.isEmpty()) {
@@ -110,7 +112,7 @@ auto FlameMod::loadIndexedPackVersion(QJsonObject& obj) -> ModPlatform::IndexedV
     file.fileId = Json::requireInteger(obj, "id");
     file.date = Json::requireString(obj, "fileDate");
     file.version = Json::requireString(obj, "displayName");
-    file.downloadUrl = Json::requireString(obj, "downloadUrl");
+    file.downloadUrl = Json::ensureString(obj, "downloadUrl");
     file.fileName = Json::requireString(obj, "fileName");
 
     auto hash_list = Json::ensureArray(obj, "hashes");
@@ -124,5 +126,9 @@ auto FlameMod::loadIndexedPackVersion(QJsonObject& obj) -> ModPlatform::IndexedV
             break;
         }
     }
+
+    if(load_changelog)
+        file.changelog = api.getModFileChangelog(file.addonId.toInt(), file.fileId.toInt());
+
     return file;
 }

launcher/modplatform/flame/FlameModIndex.h

@@ -17,6 +17,6 @@ void loadIndexedPackVersions(ModPlatform::IndexedPack& pack,
                              QJsonArray& arr,
                              const shared_qobject_ptr<QNetworkAccessManager>& network,
                              BaseInstance* inst);
-auto loadIndexedPackVersion(QJsonObject& obj) -> ModPlatform::IndexedVersion;
+auto loadIndexedPackVersion(QJsonObject& obj, bool load_changelog = false) -> ModPlatform::IndexedVersion;
 
 }  // namespace FlameMod

launcher/modplatform/helpers/NetworkModAPI.cpp

@@ -33,18 +33,14 @@ void NetworkModAPI::searchMods(CallerType* caller, SearchArgs&& args) const
 
 void NetworkModAPI::getModInfo(CallerType* caller, ModPlatform::IndexedPack& pack)
 {
-    auto id_str = pack.addonId.toString();
-    auto netJob = new NetJob(QString("%1::ModInfo").arg(id_str), APPLICATION->network());
-    auto searchUrl = getModInfoURL(id_str);
-
     auto response = new QByteArray();
-    netJob->addNetAction(Net::Download::makeByteArray(QUrl(searchUrl), response));
+    auto job = getProject(pack.addonId.toString(), response);
 
-    QObject::connect(netJob, &NetJob::succeeded, [response, &pack, caller] {
+    QObject::connect(job, &NetJob::succeeded, caller, [caller, &pack, response] {
         QJsonParseError parse_error{};
-        auto doc = QJsonDocument::fromJson(*response, &parse_error);
+        QJsonDocument doc = QJsonDocument::fromJson(*response, &parse_error);
         if (parse_error.error != QJsonParseError::NoError) {
-            qWarning() << "Error while parsing JSON response for " << pack.name << " at " << parse_error.offset
+            qWarning() << "Error while parsing JSON response from " << caller->debugName() << " at " << parse_error.offset
                        << " reason: " << parse_error.errorString();
             qWarning() << *response;
             return;
@@ -53,7 +49,7 @@ void NetworkModAPI::getModInfo(CallerType* caller, ModPlatform::IndexedPack& pac
         caller->infoRequestFinished(doc, pack);
     });
 
-    netJob->start();
+    job->start();
 }
 
 void NetworkModAPI::getVersions(CallerType* caller, VersionSearchArgs&& args) const
@@ -83,3 +79,18 @@ void NetworkModAPI::getVersions(CallerType* caller, VersionSearchArgs&& args) co
 
     netJob->start();
 }
+
+auto NetworkModAPI::getProject(QString addonId, QByteArray* response) const -> NetJob*
+{
+    auto netJob = new NetJob(QString("%1::GetProject").arg(addonId), APPLICATION->network());
+    auto searchUrl = getModInfoURL(addonId);
+
+    netJob->addNetAction(Net::Download::makeByteArray(QUrl(searchUrl), response));
+
+    QObject::connect(netJob, &NetJob::finished, [response, netJob] {
+        netJob->deleteLater();
+        delete response;
+    });
+
+    return netJob;
+}

launcher/modplatform/helpers/NetworkModAPI.h

@@ -8,6 +8,8 @@ class NetworkModAPI : public ModAPI {
     void getModInfo(CallerType* caller, ModPlatform::IndexedPack& pack) override;
     void getVersions(CallerType* caller, VersionSearchArgs&& args) const override;
 
+    auto getProject(QString addonId, QByteArray* response) const -> NetJob* override;
+
    protected:
     virtual auto getModSearchURL(SearchArgs& args) const -> QString = 0;
     virtual auto getModInfoURL(QString& id) const -> QString = 0;

launcher/modplatform/modrinth/ModrinthAPI.cpp

@@ -0,0 +1,108 @@
+#include "ModrinthAPI.h"
+
+#include "Application.h"
+#include "Json.h"
+#include "net/Upload.h"
+
+auto ModrinthAPI::currentVersion(QString hash, QString hash_format, QByteArray* response) -> NetJob::Ptr
+{
+    auto* netJob = new NetJob(QString("Modrinth::GetCurrentVersion"), APPLICATION->network());
+
+    netJob->addNetAction(Net::Download::makeByteArray(
+        QString(BuildConfig.MODRINTH_PROD_URL + "/version_file/%1?algorithm=%2").arg(hash, hash_format), response));
+
+    QObject::connect(netJob, &NetJob::finished, [response] { delete response; });
+
+    return netJob;
+}
+
+auto ModrinthAPI::currentVersions(const QStringList& hashes, QString hash_format, QByteArray* response) -> NetJob::Ptr
+{
+    auto* netJob = new NetJob(QString("Modrinth::GetCurrentVersions"), APPLICATION->network());
+
+    QJsonObject body_obj;
+
+    Json::writeStringList(body_obj, "hashes", hashes);
+    Json::writeString(body_obj, "algorithm", hash_format);
+
+    QJsonDocument body(body_obj);
+    auto body_raw = body.toJson();
+
+    netJob->addNetAction(Net::Upload::makeByteArray(QString(BuildConfig.MODRINTH_PROD_URL + "/version_files"), response, body_raw));
+
+    QObject::connect(netJob, &NetJob::finished, [response] { delete response; });
+
+    return netJob;
+}
+
+auto ModrinthAPI::latestVersion(QString hash,
+                                QString hash_format,
+                                std::list<Version> mcVersions,
+                                ModLoaderTypes loaders,
+                                QByteArray* response) -> NetJob::Ptr
+{
+    auto* netJob = new NetJob(QString("Modrinth::GetLatestVersion"), APPLICATION->network());
+
+    QJsonObject body_obj;
+
+    Json::writeStringList(body_obj, "loaders", getModLoaderStrings(loaders));
+
+    QStringList game_versions;
+    for (auto& ver : mcVersions) {
+        game_versions.append(ver.toString());
+    }
+    Json::writeStringList(body_obj, "game_versions", game_versions);
+
+    QJsonDocument body(body_obj);
+    auto body_raw = body.toJson();
+
+    netJob->addNetAction(Net::Upload::makeByteArray(
+        QString(BuildConfig.MODRINTH_PROD_URL + "/version_file/%1/update?algorithm=%2").arg(hash, hash_format), response, body_raw));
+
+    QObject::connect(netJob, &NetJob::finished, [response] { delete response; });
+
+    return netJob;
+}
+
+auto ModrinthAPI::latestVersions(const QStringList& hashes,
+                                 QString hash_format,
+                                 std::list<Version> mcVersions,
+                                 ModLoaderTypes loaders,
+                                 QByteArray* response) -> NetJob::Ptr
+{
+    auto* netJob = new NetJob(QString("Modrinth::GetLatestVersions"), APPLICATION->network());
+
+    QJsonObject body_obj;
+
+    Json::writeStringList(body_obj, "hashes", hashes);
+    Json::writeString(body_obj, "algorithm", hash_format);
+
+    Json::writeStringList(body_obj, "loaders", getModLoaderStrings(loaders));
+
+    QStringList game_versions;
+    for (auto& ver : mcVersions) {
+        game_versions.append(ver.toString());
+    }
+    Json::writeStringList(body_obj, "game_versions", game_versions);
+
+    QJsonDocument body(body_obj);
+    auto body_raw = body.toJson();
+
+    netJob->addNetAction(Net::Upload::makeByteArray(QString(BuildConfig.MODRINTH_PROD_URL + "/version_files/update"), response, body_raw));
+
+    QObject::connect(netJob, &NetJob::finished, [response] { delete response; });
+
+    return netJob;
+}
+
+auto ModrinthAPI::getProjects(QStringList addonIds, QByteArray* response) const -> NetJob*
+{
+    auto netJob = new NetJob(QString("Modrinth::GetProjects"), APPLICATION->network());
+    auto searchUrl = getMultipleModInfoURL(addonIds);
+
+    netJob->addNetAction(Net::Download::makeByteArray(QUrl(searchUrl), response));
+
+    QObject::connect(netJob, &NetJob::finished, [response, netJob] { delete response; netJob->deleteLater(); });
+
+    return netJob;
+}

launcher/modplatform/modrinth/ModrinthAPI.h

@@ -26,6 +26,29 @@
 #include <QDebug>
 
 class ModrinthAPI : public NetworkModAPI {
+   public:
+    auto currentVersion(QString hash,
+                        QString hash_format,
+                        QByteArray* response) -> NetJob::Ptr;
+
+    auto currentVersions(const QStringList& hashes,
+                         QString hash_format,
+                         QByteArray* response) -> NetJob::Ptr;
+
+    auto latestVersion(QString hash,
+                       QString hash_format,
+                       std::list<Version> mcVersions,
+                       ModLoaderTypes loaders,
+                       QByteArray* response) -> NetJob::Ptr;
+
+    auto latestVersions(const QStringList& hashes,
+                        QString hash_format,
+                        std::list<Version> mcVersions,
+                        ModLoaderTypes loaders,
+                        QByteArray* response) -> NetJob::Ptr;
+
+    auto getProjects(QStringList addonIds, QByteArray* response) const -> NetJob* override;
+
    public:
     inline auto getAuthorURL(const QString& name) const -> QString { return "https://modrinth.com/user/" + name; };
 
@@ -81,6 +104,11 @@ class ModrinthAPI : public NetworkModAPI {
         return BuildConfig.MODRINTH_PROD_URL + "/project/" + id;
     };
 
+    inline auto getMultipleModInfoURL(QStringList ids) const -> QString
+    {
+        return BuildConfig.MODRINTH_PROD_URL + QString("/projects?ids=[\"%1\"]").arg(ids.join("\",\""));
+    };
+
     inline auto getVersionsURL(VersionSearchArgs& args) const -> QString override
     {
         return QString(BuildConfig.MODRINTH_PROD_URL +

launcher/modplatform/modrinth/ModrinthCheckUpdate.cpp

@@ -0,0 +1,174 @@
+#include "ModrinthCheckUpdate.h"
+#include "ModrinthAPI.h"
+#include "ModrinthPackIndex.h"
+
+#include "FileSystem.h"
+#include "Json.h"
+
+#include "ModDownloadTask.h"
+
+static ModrinthAPI api;
+static ModPlatform::ProviderCapabilities ProviderCaps;
+
+bool ModrinthCheckUpdate::abort()
+{
+    if (m_net_job)
+        return m_net_job->abort();
+    return true;
+}
+
+/* Check for update:
+ * - Get latest version available
+ * - Compare hash of the latest version with the current hash
+ * - If equal, no updates, else, there's updates, so add to the list
+ * */
+void ModrinthCheckUpdate::executeTask()
+{
+    setStatus(tr("Preparing mods for Modrinth..."));
+    setProgress(0, 3);
+
+    QHash<QString, Mod*> mappings;
+
+    // Create all hashes
+    QStringList hashes;
+    auto best_hash_type = ProviderCaps.hashType(ModPlatform::Provider::MODRINTH).first();
+    for (auto* mod : m_mods) {
+        if (!mod->enabled()) {
+            emit checkFailed(mod, tr("Disabled mods won't be updated, to prevent mod duplication issues!"));
+            continue;
+        }
+
+        auto hash = mod->metadata()->hash;
+
+        // Sadly the API can only handle one hash type per call, se we
+        // need to generate a new hash if the current one is innadequate
+        // (though it will rarely happen, if at all)
+        if (mod->metadata()->hash_format != best_hash_type) {
+            QByteArray jar_data;
+
+            try {
+                jar_data = FS::read(mod->fileinfo().absoluteFilePath());
+            } catch (FS::FileSystemException& e) {
+                qCritical() << QString("Failed to open / read JAR file of %1").arg(mod->name());
+                qCritical() << QString("Reason: ") << e.cause();
+
+                failed(e.what());
+                return;
+            }
+
+            hash = QString(ProviderCaps.hash(ModPlatform::Provider::MODRINTH, jar_data, best_hash_type).toHex());
+        }
+
+        hashes.append(hash);
+        mappings.insert(hash, mod);
+    }
+
+    auto* response = new QByteArray();
+    auto job = api.latestVersions(hashes, best_hash_type, m_game_versions, m_loaders, response);
+
+    QEventLoop lock;
+
+    connect(job.get(), &Task::succeeded, this, [this, response, &mappings, best_hash_type, job] {
+        QJsonParseError parse_error{};
+        QJsonDocument doc = QJsonDocument::fromJson(*response, &parse_error);
+        if (parse_error.error != QJsonParseError::NoError) {
+            qWarning() << "Error while parsing JSON response from ModrinthCheckUpdate at " << parse_error.offset
+                       << " reason: " << parse_error.errorString();
+            qWarning() << *response;
+
+            failed(parse_error.errorString());
+            return;
+        }
+
+        setStatus(tr("Parsing the API response from Modrinth..."));
+        setProgress(2, 3);
+
+        try {
+            for (auto hash : mappings.keys()) {
+                auto project_obj = doc[hash].toObject();
+
+                // If the returned project is empty, but we have Modrinth metadata,
+                // it means this specific version is not available
+                if (project_obj.isEmpty()) {
+                    qDebug() << "Mod " << mappings.find(hash).value()->name() << " got an empty response.";
+                    qDebug() << "Hash: " << hash;
+
+                    emit checkFailed(
+                        mappings.find(hash).value(),
+                        tr("No valid version found for this mod. It's probably unavailable for the current game version / mod loader."));
+
+                    continue;
+                }
+
+                // Sometimes a version may have multiple files, one with "forge" and one with "fabric",
+                // so we may want to filter it
+                QString loader_filter;
+                static auto flags = { ModAPI::ModLoaderType::Forge, ModAPI::ModLoaderType::Fabric, ModAPI::ModLoaderType::Quilt };
+                for (auto flag : flags) {
+                    if (m_loaders.testFlag(flag)) {
+                        loader_filter = api.getModLoaderString(flag);
+                        break;
+                    }
+                }
+
+                // Currently, we rely on a couple heuristics to determine whether an update is actually available or not:
+                // - The file needs to be preferred: It is either the primary file, or the one found via (explicit) usage of the loader_filter
+                // - The version reported by the JAR is different from the version reported by the indexed version (it's usually the case)
+                // Such is the pain of having arbitrary files for a given version .-.
+
+                auto project_ver = Modrinth::loadIndexedPackVersion(project_obj, best_hash_type, loader_filter);
+                if (project_ver.downloadUrl.isEmpty()) {
+                    qCritical() << "Modrinth mod without download url!";
+                    qCritical() << project_ver.fileName;
+
+                    emit checkFailed(mappings.find(hash).value(), tr("Mod has an empty download URL"));
+
+                    continue;
+                }
+
+                auto mod_iter = mappings.find(hash);
+                if (mod_iter == mappings.end()) {
+                    qCritical() << "Failed to remap mod from Modrinth!";
+                    continue;
+                }
+                auto mod = *mod_iter;
+
+                auto key = project_ver.hash;
+                if ((key != hash && project_ver.is_preferred) || (mod->status() == ModStatus::NotInstalled)) {
+                    if (mod->version() == project_ver.version_number)
+                        continue;
+
+                    // Fake pack with the necessary info to pass to the download task :)
+                    ModPlatform::IndexedPack pack;
+                    pack.name = mod->name();
+                    pack.slug = mod->metadata()->slug;
+                    pack.addonId = mod->metadata()->project_id;
+                    pack.websiteUrl = mod->homeurl();
+                    for (auto& author : mod->authors())
+                        pack.authors.append({ author });
+                    pack.description = mod->description();
+                    pack.provider = ModPlatform::Provider::MODRINTH;
+
+                    auto download_task = new ModDownloadTask(pack, project_ver, m_mods_folder);
+
+                    m_updatable.emplace_back(pack.name, hash, mod->version(), project_ver.version_number, project_ver.changelog,
+                                             ModPlatform::Provider::MODRINTH, download_task);
+                }
+            }
+        } catch (Json::JsonException& e) {
+            failed(e.cause() + " : " + e.what());
+        }
+    });
+
+    connect(job.get(), &Task::finished, &lock, &QEventLoop::quit);
+
+    setStatus(tr("Waiting for the API response from Modrinth..."));
+    setProgress(1, 3);
+
+    m_net_job = job.get();
+    job->start();
+
+    lock.exec();
+
+    emitSucceeded();
+}

launcher/modplatform/modrinth/ModrinthCheckUpdate.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "Application.h"
+#include "modplatform/CheckUpdateTask.h"
+#include "net/NetJob.h"
+
+class ModrinthCheckUpdate : public CheckUpdateTask {
+    Q_OBJECT
+
+   public:
+    ModrinthCheckUpdate(QList<Mod*>& mods, std::list<Version>& mcVersions, ModAPI::ModLoaderTypes loaders, std::shared_ptr<ModFolderModel> mods_folder)
+        : CheckUpdateTask(mods, mcVersions, loaders, mods_folder)
+    {}
+
+   public slots:
+    bool abort() override;
+
+   protected slots:
+    void executeTask() override;
+
+   private:
+    NetJob* m_net_job = nullptr;
+};

launcher/modplatform/modrinth/ModrinthPackIndex.cpp

@@ -29,13 +29,16 @@ static ModPlatform::ProviderCapabilities ProviderCaps;
 
 void Modrinth::loadIndexedPack(ModPlatform::IndexedPack& pack, QJsonObject& obj)
 {
-    pack.addonId = Json::requireString(obj, "project_id");
+    pack.addonId = Json::ensureString(obj, "project_id");
+    if (pack.addonId.toString().isEmpty())
+        pack.addonId = Json::requireString(obj, "id");
+
     pack.provider = ModPlatform::Provider::MODRINTH;
     pack.name = Json::requireString(obj, "title");
     
-    QString slug = Json::ensureString(obj, "slug", "");
+    pack.slug = Json::ensureString(obj, "slug", "");
-    if (!slug.isEmpty())
+    if (!pack.slug.isEmpty())
-        pack.websiteUrl = "https://modrinth.com/mod/" + Json::ensureString(obj, "slug", "");
+        pack.websiteUrl = "https://modrinth.com/mod/" + pack.slug;
     else
         pack.websiteUrl = "";
 
@@ -45,7 +48,7 @@ void Modrinth::loadIndexedPack(ModPlatform::IndexedPack& pack, QJsonObject& obj)
     pack.logoName = pack.addonId.toString();
 
     ModPlatform::ModpackAuthor modAuthor;
-    modAuthor.name = Json::requireString(obj, "author");
+    modAuthor.name = Json::ensureString(obj, "author", QObject::tr("No author(s)"));
     modAuthor.url = api.getAuthorURL(modAuthor.name);
     pack.authors.append(modAuthor);
 
@@ -111,7 +114,7 @@ void Modrinth::loadIndexedPackVersions(ModPlatform::IndexedPack& pack,
     pack.versionsLoaded = true;
 }
 
-auto Modrinth::loadIndexedPackVersion(QJsonObject &obj) -> ModPlatform::IndexedVersion
+auto Modrinth::loadIndexedPackVersion(QJsonObject &obj, QString preferred_hash_type, QString preferred_file_name) -> ModPlatform::IndexedVersion
 {
     ModPlatform::IndexedVersion file;
 
@@ -130,6 +133,8 @@ auto Modrinth::loadIndexedPackVersion(QJsonObject &obj) -> ModPlatform::IndexedV
         file.loaders.append(loader.toString());
     }
     file.version = Json::requireString(obj, "name");
+    file.version_number = Json::requireString(obj, "version_number");
+    file.changelog = Json::requireString(obj, "changelog");
 
     auto files = Json::requireArray(obj, "files");
     int i = 0;
@@ -142,6 +147,11 @@ auto Modrinth::loadIndexedPackVersion(QJsonObject &obj) -> ModPlatform::IndexedV
         auto parent = files[i].toObject();
         auto fileName = Json::requireString(parent, "filename");
 
+        if (!preferred_file_name.isEmpty() && fileName.contains(preferred_file_name)) {
+            file.is_preferred = true;
+            break;
+        }
+
         // Grab the primary file, if available
         if (Json::requireBoolean(parent, "primary"))
             break;
@@ -153,13 +163,20 @@ auto Modrinth::loadIndexedPackVersion(QJsonObject &obj) -> ModPlatform::IndexedV
     if (parent.contains("url")) {
         file.downloadUrl = Json::requireString(parent, "url");
         file.fileName = Json::requireString(parent, "filename");
+        file.is_preferred = Json::requireBoolean(parent, "primary") || (files.count() == 1);
         auto hash_list = Json::requireObject(parent, "hashes");
-        auto hash_types = ProviderCaps.hashType(ModPlatform::Provider::MODRINTH);
+        
-        for (auto& hash_type : hash_types) {
+        if (hash_list.contains(preferred_hash_type)) {
-            if (hash_list.contains(hash_type)) {
+            file.hash = Json::requireString(hash_list, preferred_hash_type);
-                file.hash = Json::requireString(hash_list, hash_type);
+            file.hash_type = preferred_hash_type;
-                file.hash_type = hash_type;
+        } else {
-                break;
+            auto hash_types = ProviderCaps.hashType(ModPlatform::Provider::MODRINTH);
+            for (auto& hash_type : hash_types) {
+                if (hash_list.contains(hash_type)) {
+                    file.hash = Json::requireString(hash_list, hash_type);
+                    file.hash_type = hash_type;
+                    break;
+                }
             }
         }
 

launcher/modplatform/modrinth/ModrinthPackIndex.h

@@ -30,6 +30,6 @@ void loadIndexedPackVersions(ModPlatform::IndexedPack& pack,
                              QJsonArray& arr,
                              const shared_qobject_ptr<QNetworkAccessManager>& network,
                              BaseInstance* inst);
-auto loadIndexedPackVersion(QJsonObject& obj) -> ModPlatform::IndexedVersion;
+auto loadIndexedPackVersion(QJsonObject& obj, QString hash_type = "sha512", QString filename_prefer = "") -> ModPlatform::IndexedVersion;
 
 }  // namespace Modrinth

launcher/modplatform/packwiz/Packwiz.cpp

@@ -55,11 +55,11 @@ auto getRealIndexName(QDir& index_dir, QString normalized_fname, bool should_fin
 }
 
 // Helpers
-static inline auto indexFileName(QString const& mod_name) -> QString
+static inline auto indexFileName(QString const& mod_slug) -> QString
 {
-    if(mod_name.endsWith(".pw.toml"))
+    if(mod_slug.endsWith(".pw.toml"))
-        return mod_name;
+        return mod_slug;
-    return QString("%1.pw.toml").arg(mod_name);
+    return QString("%1.pw.toml").arg(mod_slug);
 }
 
 static ModPlatform::ProviderCapabilities ProviderCaps;
@@ -95,6 +95,7 @@ auto V1::createModFormat(QDir& index_dir, ModPlatform::IndexedPack& mod_pack, Mo
 {
     Mod mod;
 
+    mod.slug = mod_pack.slug;
     mod.name = mod_pack.name;
     mod.filename = mod_version.fileName;
 
@@ -116,12 +117,10 @@ auto V1::createModFormat(QDir& index_dir, ModPlatform::IndexedPack& mod_pack, Mo
     return mod;
 }
 
-auto V1::createModFormat(QDir& index_dir, ::Mod& internal_mod) -> Mod
+auto V1::createModFormat(QDir& index_dir, ::Mod& internal_mod, QString slug) -> Mod
 {
-    auto mod_name = internal_mod.name();
-
     // Try getting metadata if it exists
-    Mod mod { getIndexForMod(index_dir, mod_name) };
+    Mod mod { getIndexForMod(index_dir, slug) };
     if(mod.isValid())
         return mod;
 
@@ -139,11 +138,14 @@ void V1::updateModIndex(QDir& index_dir, Mod& mod)
 
     // Ensure the corresponding mod's info exists, and create it if not
 
-    auto normalized_fname = indexFileName(mod.name);
+    auto normalized_fname = indexFileName(mod.slug);
     auto real_fname = getRealIndexName(index_dir, normalized_fname);
 
     QFile index_file(index_dir.absoluteFilePath(real_fname));
 
+    if (real_fname != normalized_fname)
+        index_file.rename(normalized_fname);
+
     // There's already data on there!
     // TODO: We should do more stuff here, as the user is likely trying to
     // override a file. In this case, check versions and ask the user what
@@ -184,33 +186,46 @@ void V1::updateModIndex(QDir& index_dir, Mod& mod)
         }
     }
 
+    index_file.flush();
     index_file.close();
 }
 
-void V1::deleteModIndex(QDir& index_dir, QString& mod_name)
+void V1::deleteModIndex(QDir& index_dir, QString& mod_slug)
 {
-    auto normalized_fname = indexFileName(mod_name);
+    auto normalized_fname = indexFileName(mod_slug);
     auto real_fname = getRealIndexName(index_dir, normalized_fname);
     if (real_fname.isEmpty())
         return;
 
     QFile index_file(index_dir.absoluteFilePath(real_fname));
 
-    if(!index_file.exists()){
+    if (!index_file.exists()) {
-        qWarning() << QString("Tried to delete non-existent mod metadata for %1!").arg(mod_name);
+        qWarning() << QString("Tried to delete non-existent mod metadata for %1!").arg(mod_slug);
         return;
     }
 
-    if(!index_file.remove()){
+    if (!index_file.remove()) {
-        qWarning() << QString("Failed to remove metadata for mod %1!").arg(mod_name);
+        qWarning() << QString("Failed to remove metadata for mod %1!").arg(mod_slug);
     }
 }
 
-auto V1::getIndexForMod(QDir& index_dir, QString& index_file_name) -> Mod
+void V1::deleteModIndex(QDir& index_dir, QVariant& mod_id)
+{
+    for (auto& file_name : index_dir.entryList(QDir::Filter::Files)) {
+        auto mod = getIndexForMod(index_dir, file_name);
+
+        if (mod.mod_id() == mod_id) {
+            deleteModIndex(index_dir, mod.name);
+            break;
+        }
+    }
+}
+
+auto V1::getIndexForMod(QDir& index_dir, QString slug) -> Mod
 {
     Mod mod;
 
-    auto normalized_fname = indexFileName(index_file_name);
+    auto normalized_fname = indexFileName(slug);
     auto real_fname = getRealIndexName(index_dir, normalized_fname, true);
     if (real_fname.isEmpty())
         return {};
@@ -218,7 +233,7 @@ auto V1::getIndexForMod(QDir& index_dir, QString& index_file_name) -> Mod
     QFile index_file(index_dir.absoluteFilePath(real_fname));
 
     if (!index_file.open(QIODevice::ReadOnly)) {
-        qWarning() << QString("Failed to open mod metadata for %1").arg(index_file_name);
+        qWarning() << QString("Failed to open mod metadata for %1").arg(slug);
         return {};
     }
 
@@ -232,11 +247,13 @@ auto V1::getIndexForMod(QDir& index_dir, QString& index_file_name) -> Mod
     index_file.close();
 
     if (!table) {
-        qWarning() << QString("Could not open file %1!").arg(indexFileName(index_file_name));
+        qWarning() << QString("Could not open file %1!").arg(normalized_fname);
         qWarning() << "Reason: " << QString(errbuf);
         return {};
     }
 
+    mod.slug = slug;
+
     {  // Basic info
         mod.name = stringEntry(table, "name");
         mod.filename = stringEntry(table, "filename");
@@ -286,4 +303,16 @@ auto V1::getIndexForMod(QDir& index_dir, QString& index_file_name) -> Mod
     return mod;
 }
 
-} // namespace Packwiz
+auto V1::getIndexForMod(QDir& index_dir, QVariant& mod_id) -> Mod
+{
+    for (auto& file_name : index_dir.entryList(QDir::Filter::Files)) {
+        auto mod = getIndexForMod(index_dir, file_name);
+
+        if (mod.mod_id() == mod_id)
+            return mod;
+    }
+
+    return {};
+}
+
+}  // namespace Packwiz

launcher/modplatform/packwiz/Packwiz.h

@@ -40,6 +40,7 @@ auto intEntry(toml_table_t* parent, const char* entry_name) -> int;
 class V1 {
    public:
     struct Mod {
+        QString slug {};
         QString name {};
         QString filename {};
         // FIXME: make side an enum
@@ -58,7 +59,7 @@ class V1 {
 
        public:
         // This is a totally heuristic, but should work for now.
-        auto isValid() const -> bool { return !name.isEmpty() && !project_id.isNull(); }
+        auto isValid() const -> bool { return !slug.isEmpty() && !project_id.isNull(); }
 
         // Different providers can use different names for the same thing
         // Modrinth-specific
@@ -71,9 +72,9 @@ class V1 {
      * */
     static auto createModFormat(QDir& index_dir, ModPlatform::IndexedPack& mod_pack, ModPlatform::IndexedVersion& mod_version) -> Mod;
     /* Generates the object representing the information in a mod.pw.toml file via
-     * its common representation in the launcher.
+     * its common representation in the launcher, plus a necessary slug.
      * */
-    static auto createModFormat(QDir& index_dir, ::Mod& internal_mod) -> Mod;
+    static auto createModFormat(QDir& index_dir, ::Mod& internal_mod, QString slug) -> Mod;
 
     /* Updates the mod index for the provided mod.
      * This creates a new index if one does not exist already
@@ -81,13 +82,21 @@ class V1 {
      * */
     static void updateModIndex(QDir& index_dir, Mod& mod);
 
-    /* Deletes the metadata for the mod with the given name. If the metadata doesn't exist, it does nothing. */
+    /* Deletes the metadata for the mod with the given slug. If the metadata doesn't exist, it does nothing. */
-    static void deleteModIndex(QDir& index_dir, QString& mod_name);
+    static void deleteModIndex(QDir& index_dir, QString& mod_slug);
 
-    /* Gets the metadata for a mod with a particular name.
+    /* Deletes the metadata for the mod with the given id. If the metadata doesn't exist, it does nothing. */
+    static void deleteModIndex(QDir& index_dir, QVariant& mod_id);
+
+    /* Gets the metadata for a mod with a particular file name.
      * If the mod doesn't have a metadata, it simply returns an empty Mod object.
      * */
-    static auto getIndexForMod(QDir& index_dir, QString& index_file_name) -> Mod;
+    static auto getIndexForMod(QDir& index_dir, QString slug) -> Mod;
+
+    /* Gets the metadata for a mod with a particular id.
+     * If the mod doesn't have a metadata, it simply returns an empty Mod object.
+     * */
+    static auto getIndexForMod(QDir& index_dir, QVariant& mod_id) -> Mod;
 };
 
 } // namespace Packwiz

launcher/modplatform/packwiz/Packwiz_test.cpp

@@ -32,10 +32,11 @@ class PackwizTest : public QObject {
         QString source = QFINDTESTDATA("testdata");
 
         QDir index_dir(source);
-        QString name_mod("borderless-mining.pw.toml");
+        QString slug_mod("borderless-mining");
-        QVERIFY(index_dir.entryList().contains(name_mod));
+        QString file_name = slug_mod + ".pw.toml";
+        QVERIFY(index_dir.entryList().contains(file_name));
 
-        auto metadata = Packwiz::V1::getIndexForMod(index_dir, name_mod);
+        auto metadata = Packwiz::V1::getIndexForMod(index_dir, slug_mod);
 
         QVERIFY(metadata.isValid());
 

launcher/net/Upload.cpp

@@ -43,6 +43,16 @@
 
 namespace Net {
 
+    bool Upload::abort()
+    {
+        if (m_reply) {
+            m_reply->abort();
+        } else {
+            m_state = State::AbortedByUser;
+        }
+        return true;
+    }
+
     void Upload::downloadProgress(qint64 bytesReceived, qint64 bytesTotal) {
         setProgress(bytesReceived, bytesTotal);
     }

launcher/net/Upload.h

@@ -46,6 +46,8 @@ namespace Net {
 
     public:
         static Upload::Ptr makeByteArray(QUrl url, QByteArray *output, QByteArray m_post_data);
+        auto abort() -> bool override;
+        auto canAbort() const -> bool override { return true; };
 
     protected slots:
         void downloadProgress(qint64 bytesReceived, qint64 bytesTotal) override;

launcher/tasks/MultipleOptionsTask.cpp

@@ -0,0 +1,48 @@
+#include "MultipleOptionsTask.h"
+
+#include <QDebug>
+
+MultipleOptionsTask::MultipleOptionsTask(QObject* parent, const QString& task_name) : SequentialTask(parent, task_name) {}
+
+void MultipleOptionsTask::startNext()
+{
+    Task* previous = nullptr;
+    if (m_currentIndex != -1) {
+        previous = m_queue[m_currentIndex].get();
+        disconnect(previous, 0, this, 0);
+    }
+
+    m_currentIndex++;
+    if ((previous && previous->wasSuccessful())) {
+        emitSucceeded();
+        return;
+    }
+
+    Task::Ptr next = m_queue[m_currentIndex];
+
+    connect(next.get(), &Task::failed, this, &MultipleOptionsTask::subTaskFailed);
+    connect(next.get(), &Task::succeeded, this, &MultipleOptionsTask::startNext);
+
+    connect(next.get(), &Task::status, this, &MultipleOptionsTask::subTaskStatus);
+    connect(next.get(), &Task::stepStatus, this, &MultipleOptionsTask::subTaskStatus);
+    
+    connect(next.get(), &Task::progress, this, &MultipleOptionsTask::subTaskProgress);
+
+    qDebug() << QString("Making attemp %1 out of %2").arg(m_currentIndex + 1).arg(m_queue.size());
+    setStatus(tr("Making attempt #%1 out of %2").arg(m_currentIndex + 1).arg(m_queue.size()));
+    setStepStatus(next->isMultiStep() ? next->getStepStatus() : next->getStatus());
+
+    next->start();
+}
+
+void MultipleOptionsTask::subTaskFailed(QString const& reason)
+{
+    qDebug() << QString("Failed attempt #%1 of %2. Reason: %3").arg(m_currentIndex + 1).arg(m_queue.size()).arg(reason);
+    if(m_currentIndex < m_queue.size() - 1) {
+        startNext();
+        return;
+    }
+
+    qWarning() << QString("All attempts have failed!");
+    emitFailed();
+}

launcher/tasks/MultipleOptionsTask.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "SequentialTask.h"
+
+/* This task type will attempt to do run each of it's subtasks in sequence,
+ * until one of them succeeds. When that happens, the remaining tasks will not run.
+ * */
+class MultipleOptionsTask : public SequentialTask
+{
+    Q_OBJECT
+public:
+    explicit MultipleOptionsTask(QObject *parent = nullptr, const QString& task_name = "");
+    virtual ~MultipleOptionsTask() = default;
+
+private
+slots:
+    void startNext() override;
+    void subTaskFailed(const QString &msg) override;
+};

launcher/tasks/SequentialTask.cpp

@@ -1,5 +1,7 @@
 #include "SequentialTask.h"
 
+#include <QDebug>
+
 SequentialTask::SequentialTask(QObject* parent, const QString& task_name) : Task(parent), m_name(task_name), m_currentIndex(-1) {}
 
 SequentialTask::~SequentialTask()
@@ -39,14 +41,15 @@ bool SequentialTask::abort()
             emit aborted();
             emit finished();
         }
-        m_queue.clear();
+
+        m_aborted = true;
         return true;
     }
 
     bool succeeded = m_queue[m_currentIndex]->abort();
-    m_queue.clear();
+    m_aborted = succeeded;
 
-    if(succeeded)
+    if (succeeded)
         emitAborted();
 
     return succeeded;
@@ -54,10 +57,14 @@ bool SequentialTask::abort()
 
 void SequentialTask::startNext()
 {
-    if (m_currentIndex != -1) {
+    if (m_aborted)
-        Task::Ptr previous = m_queue[m_currentIndex];
+        return;
+
+    if (m_currentIndex != -1 && m_currentIndex < m_queue.size()) {
+        Task::Ptr previous = m_queue.at(m_currentIndex);
         disconnect(previous.get(), 0, this, 0);
     }
+
     m_currentIndex++;
     if (m_queue.isEmpty() || m_currentIndex >= m_queue.size()) {
         emitSucceeded();
@@ -76,6 +83,8 @@ void SequentialTask::startNext()
     setStatus(tr("Executing task %1 out of %2").arg(m_currentIndex + 1).arg(m_queue.size()));
     setStepStatus(next->isMultiStep() ? next->getStepStatus() : next->getStatus());
 
+    setProgress(m_currentIndex + 1, m_queue.count());
+
     next->start();
 }
 
@@ -93,7 +102,6 @@ void SequentialTask::subTaskProgress(qint64 current, qint64 total)
         setProgress(0, 100);
         return;
     }
-    setProgress(m_currentIndex + 1, m_queue.count());
 
     m_stepProgress = current;
     m_stepTotalProgress = total;

launcher/tasks/SequentialTask.h

@@ -20,17 +20,17 @@ public:
 
     void addTask(Task::Ptr task);
 
-protected slots:
-    void executeTask() override;
 public slots:
     bool abort() override;
 
-private
+protected
 slots:
-    void startNext();
+    void executeTask() override;
-    void subTaskFailed(const QString &msg);
+
-    void subTaskStatus(const QString &msg);
+    virtual void startNext();
-    void subTaskProgress(qint64 current, qint64 total);
+    virtual void subTaskFailed(const QString &msg);
+    virtual void subTaskStatus(const QString &msg);
+    virtual void subTaskProgress(qint64 current, qint64 total);
 
 protected:
     void setStepStatus(QString status) { m_step_status = status; emit stepStatus(status); };
@@ -44,4 +44,6 @@ protected:
 
     qint64 m_stepProgress = 0;
     qint64 m_stepTotalProgress = 100;
+
+    bool m_aborted = false;
 };

launcher/ui/dialogs/ChooseProviderDialog.cpp

@@ -0,0 +1,96 @@
+#include "ChooseProviderDialog.h"
+#include "ui_ChooseProviderDialog.h"
+
+#include <QPushButton>
+#include <QRadioButton>
+
+#include "modplatform/ModIndex.h"
+
+static ModPlatform::ProviderCapabilities ProviderCaps;
+
+ChooseProviderDialog::ChooseProviderDialog(QWidget* parent, bool single_choice, bool allow_skipping)
+    : QDialog(parent), ui(new Ui::ChooseProviderDialog)
+{
+    ui->setupUi(this);
+
+    addProviders();
+    m_providers.button(0)->click();
+
+    connect(ui->skipOneButton, &QPushButton::clicked, this, &ChooseProviderDialog::skipOne);
+    connect(ui->skipAllButton, &QPushButton::clicked, this, &ChooseProviderDialog::skipAll);
+
+    connect(ui->confirmOneButton, &QPushButton::clicked, this, &ChooseProviderDialog::confirmOne);
+    connect(ui->confirmAllButton, &QPushButton::clicked, this, &ChooseProviderDialog::confirmAll);
+
+    if (single_choice) {
+        ui->providersLayout->removeWidget(ui->skipAllButton);
+        ui->providersLayout->removeWidget(ui->confirmAllButton);
+    }
+
+    if (!allow_skipping) {
+        ui->providersLayout->removeWidget(ui->skipOneButton);
+        ui->providersLayout->removeWidget(ui->skipAllButton);
+    }
+}
+
+ChooseProviderDialog::~ChooseProviderDialog()
+{
+    delete ui;
+}
+
+void ChooseProviderDialog::setDescription(QString desc)
+{
+    ui->explanationLabel->setText(desc);
+}
+
+void ChooseProviderDialog::skipOne()
+{
+    reject();
+}
+void ChooseProviderDialog::skipAll()
+{
+    m_response.skip_all = true;
+    reject();
+}
+
+void ChooseProviderDialog::confirmOne()
+{
+    m_response.chosen = getSelectedProvider();
+    m_response.try_others = ui->tryOthersCheckbox->isChecked();
+    accept();
+}
+void ChooseProviderDialog::confirmAll()
+{
+    m_response.chosen = getSelectedProvider();
+    m_response.confirm_all = true;
+    m_response.try_others = ui->tryOthersCheckbox->isChecked();
+    accept();
+}
+
+auto ChooseProviderDialog::getSelectedProvider() const -> ModPlatform::Provider
+{
+    return ModPlatform::Provider(m_providers.checkedId());
+}
+
+void ChooseProviderDialog::addProviders()
+{
+    int btn_index = 0;
+    QRadioButton* btn;
+
+    for (auto& provider : { ModPlatform::Provider::MODRINTH, ModPlatform::Provider::FLAME }) {
+        btn = new QRadioButton(ProviderCaps.readableName(provider), this);
+        m_providers.addButton(btn, btn_index++);
+        ui->providersLayout->addWidget(btn);
+    }
+}
+
+void ChooseProviderDialog::disableInput()
+{
+    for (auto& btn : m_providers.buttons())
+        btn->setEnabled(false);
+
+    ui->skipOneButton->setEnabled(false);
+    ui->skipAllButton->setEnabled(false);
+    ui->confirmOneButton->setEnabled(false);
+    ui->confirmAllButton->setEnabled(false);
+}

launcher/ui/dialogs/ChooseProviderDialog.h

@@ -0,0 +1,56 @@
+#pragma once
+
+#include <QButtonGroup>
+#include <QDialog>
+
+namespace Ui {
+class ChooseProviderDialog;
+}
+
+namespace ModPlatform {
+enum class Provider;
+}
+
+class Mod;
+class NetJob;
+class ModUpdateDialog;
+
+class ChooseProviderDialog : public QDialog {
+    Q_OBJECT
+
+    struct Response {
+        bool skip_all = false;
+        bool confirm_all = false;
+
+        bool try_others = false;
+
+        ModPlatform::Provider chosen;
+    };
+
+   public:
+    explicit ChooseProviderDialog(QWidget* parent, bool single_choice = false, bool allow_skipping = true);
+    ~ChooseProviderDialog();
+
+    auto getResponse() const -> Response { return m_response; }
+
+    void setDescription(QString desc);
+
+   private slots:
+    void skipOne();
+    void skipAll();
+    void confirmOne();
+    void confirmAll();
+
+   private:
+    void addProviders();
+    void disableInput();
+
+    auto getSelectedProvider() const -> ModPlatform::Provider;
+
+   private:
+    Ui::ChooseProviderDialog* ui;
+
+    QButtonGroup m_providers;
+
+    Response m_response;
+};

launcher/ui/dialogs/ChooseProviderDialog.ui

@@ -0,0 +1,89 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>ChooseProviderDialog</class>
+ <widget class="QDialog" name="ChooseProviderDialog">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>453</width>
+    <height>197</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>Choose a mod provider</string>
+  </property>
+  <layout class="QGridLayout" name="gridLayout">
+   <item row="0" column="0" colspan="2">
+    <widget class="QLabel" name="explanationLabel">
+     <property name="alignment">
+      <set>Qt::AlignJustify|Qt::AlignTop</set>
+     </property>
+     <property name="wordWrap">
+      <bool>true</bool>
+     </property>
+     <property name="indent">
+      <number>-1</number>
+     </property>
+    </widget>
+   </item>
+   <item row="1" column="0" colspan="2">
+    <layout class="QFormLayout" name="providersLayout">
+     <property name="labelAlignment">
+      <set>Qt::AlignHCenter|Qt::AlignTop</set>
+     </property>
+     <property name="formAlignment">
+      <set>Qt::AlignHCenter|Qt::AlignTop</set>
+     </property>
+    </layout>
+   </item>
+   <item row="4" column="0" colspan="2">
+    <layout class="QHBoxLayout" name="buttonsLayout">
+     <item>
+      <widget class="QPushButton" name="skipOneButton">
+       <property name="text">
+        <string>Skip this mod</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <widget class="QPushButton" name="skipAllButton">
+       <property name="text">
+        <string>Skip all</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <widget class="QPushButton" name="confirmAllButton">
+       <property name="text">
+        <string>Confirm for all</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <widget class="QPushButton" name="confirmOneButton">
+       <property name="text">
+        <string>Confirm</string>
+       </property>
+       <property name="default">
+        <bool>true</bool>
+       </property>
+      </widget>
+     </item>
+    </layout>
+   </item>
+   <item row="3" column="0">
+    <widget class="QCheckBox" name="tryOthersCheckbox">
+     <property name="text">
+      <string>Try to automatically use other providers if the chosen one fails</string>
+     </property>
+     <property name="checked">
+      <bool>true</bool>
+     </property>
+    </widget>
+   </item>
+  </layout>
+ </widget>
+ <resources/>
+ <connections/>
+</ui>

launcher/ui/dialogs/ModUpdateDialog.cpp

@@ -0,0 +1,408 @@
+#include "ModUpdateDialog.h"
+#include "ChooseProviderDialog.h"
+#include "CustomMessageBox.h"
+#include "ProgressDialog.h"
+#include "ScrollMessageBox.h"
+#include "ui_ReviewMessageBox.h"
+
+#include "FileSystem.h"
+#include "Json.h"
+
+#include "tasks/ConcurrentTask.h"
+
+#include "minecraft/MinecraftInstance.h"
+#include "minecraft/PackProfile.h"
+
+#include "modplatform/EnsureMetadataTask.h"
+#include "modplatform/flame/FlameCheckUpdate.h"
+#include "modplatform/modrinth/ModrinthCheckUpdate.h"
+
+#include <HoeDown.h>
+#include <QTextBrowser>
+#include <QTreeWidgetItem>
+
+static ModPlatform::ProviderCapabilities ProviderCaps;
+
+static std::list<Version> mcVersions(BaseInstance* inst)
+{
+    return { static_cast<MinecraftInstance*>(inst)->getPackProfile()->getComponent("net.minecraft")->getVersion() };
+}
+
+static ModAPI::ModLoaderTypes mcLoaders(BaseInstance* inst)
+{
+    return { static_cast<MinecraftInstance*>(inst)->getPackProfile()->getModLoaders() };
+}
+
+ModUpdateDialog::ModUpdateDialog(QWidget* parent,
+                                 BaseInstance* instance,
+                                 const std::shared_ptr<ModFolderModel> mods,
+                                 QList<Mod::Ptr>& search_for)
+    : ReviewMessageBox(parent, tr("Confirm mods to update"), "")
+    , m_parent(parent)
+    , m_mod_model(mods)
+    , m_candidates(search_for)
+    , m_second_try_metadata(new ConcurrentTask())
+    , m_instance(instance)
+{
+    ReviewMessageBox::setGeometry(0, 0, 800, 600);
+
+    ui->explainLabel->setText(tr("You're about to update the following mods:"));
+    ui->onlyCheckedLabel->setText(tr("Only mods with a check will be updated!"));
+}
+
+void ModUpdateDialog::checkCandidates()
+{
+    // Ensure mods have valid metadata
+    auto went_well = ensureMetadata();
+    if (!went_well) {
+        m_aborted = true;
+        return;
+    }
+
+    // Report failed metadata generation
+    if (!m_failed_metadata.empty()) {
+        QString text;
+        for (const auto& failed : m_failed_metadata) {
+            const auto& mod = std::get<0>(failed);
+            const auto& reason = std::get<1>(failed);
+            text += tr("Mod name: %1<br>File name: %2<br>Reason: %3<br><br>").arg(mod->name(), mod->fileinfo().fileName(), reason);
+        }
+
+        ScrollMessageBox message_dialog(m_parent, tr("Metadata generation failed"),
+                                        tr("Could not generate metadata for the following mods:<br>"
+                                           "Do you wish to proceed without those mods?"),
+                                        text);
+        message_dialog.setModal(true);
+        if (message_dialog.exec() == QDialog::Rejected) {
+            m_aborted = true;
+            QMetaObject::invokeMethod(this, "reject", Qt::QueuedConnection);
+            return;
+        }
+    }
+
+    auto versions = mcVersions(m_instance);
+    auto loaders = mcLoaders(m_instance);
+
+    SequentialTask check_task(m_parent, tr("Checking for updates"));
+
+    if (!m_modrinth_to_update.empty()) {
+        m_modrinth_check_task = new ModrinthCheckUpdate(m_modrinth_to_update, versions, loaders, m_mod_model);
+        connect(m_modrinth_check_task, &CheckUpdateTask::checkFailed, this,
+                [this](Mod* mod, QString reason, QUrl recover_url) { m_failed_check_update.append({mod, reason, recover_url}); });
+        check_task.addTask(m_modrinth_check_task);
+    }
+
+    if (!m_flame_to_update.empty()) {
+        m_flame_check_task = new FlameCheckUpdate(m_flame_to_update, versions, loaders, m_mod_model);
+        connect(m_flame_check_task, &CheckUpdateTask::checkFailed, this,
+                [this](Mod* mod, QString reason, QUrl recover_url) { m_failed_check_update.append({mod, reason, recover_url}); });
+        check_task.addTask(m_flame_check_task);
+    }
+
+    connect(&check_task, &Task::failed, this,
+            [&](QString reason) { CustomMessageBox::selectable(this, tr("Error"), reason, QMessageBox::Critical)->exec(); });
+
+    connect(&check_task, &Task::succeeded, this, [&]() {
+        QStringList warnings = check_task.warnings();
+        if (warnings.count()) {
+            CustomMessageBox::selectable(this, tr("Warnings"), warnings.join('\n'), QMessageBox::Warning)->exec();
+        }
+    });
+
+    // Check for updates
+    ProgressDialog progress_dialog(m_parent);
+    progress_dialog.setSkipButton(true, tr("Abort"));
+    progress_dialog.setWindowTitle(tr("Checking for updates..."));
+    auto ret = progress_dialog.execWithTask(&check_task);
+
+    // If the dialog was skipped / some download error happened
+    if (ret == QDialog::DialogCode::Rejected) {
+        m_aborted = true;
+        QMetaObject::invokeMethod(this, "reject", Qt::QueuedConnection);
+        return;
+    }
+
+    // Add found updates for Modrinth
+    if (m_modrinth_check_task) {
+        auto modrinth_updates = m_modrinth_check_task->getUpdatable();
+        for (auto& updatable : modrinth_updates) {
+            qDebug() << QString("Mod %1 has an update available!").arg(updatable.name);
+
+            appendMod(updatable);
+            m_tasks.insert(updatable.name, updatable.download);
+        }
+    }
+
+    // Add found updated for Flame
+    if (m_flame_check_task) {
+        auto flame_updates = m_flame_check_task->getUpdatable();
+        for (auto& updatable : flame_updates) {
+            qDebug() << QString("Mod %1 has an update available!").arg(updatable.name);
+
+            appendMod(updatable);
+            m_tasks.insert(updatable.name, updatable.download);
+        }
+    }
+
+    // Report failed update checking
+    if (!m_failed_check_update.empty()) {
+        QString text;
+        for (const auto& failed : m_failed_check_update) {
+            const auto& mod = std::get<0>(failed);
+            const auto& reason = std::get<1>(failed);
+            const auto& recover_url = std::get<2>(failed);
+
+            qDebug() << mod->name() << " failed to check for updates!";
+
+            text += tr("Mod name: %1").arg(mod->name()) + "<br>";
+            if (!reason.isEmpty())
+                text += tr("Reason: %1").arg(reason) + "<br>";
+            if (!recover_url.isEmpty())
+                text += tr("Possible solution: ") + tr("Getting the latest version manually:") + "<br>" +
+                        QString("<a href='%1'>").arg(recover_url.toString()) + recover_url.toString() + "</a><br>";
+            text += "<br>";
+        }
+
+        ScrollMessageBox message_dialog(m_parent, tr("Failed to check for updates"),
+                                        tr("Could not check or get the following mods for updates:<br>"
+                                           "Do you wish to proceed without those mods?"),
+                                        text);
+        message_dialog.setModal(true);
+        if (message_dialog.exec() == QDialog::Rejected) {
+            m_aborted = true;
+            QMetaObject::invokeMethod(this, "reject", Qt::QueuedConnection);
+            return;
+        }
+    }
+
+    // If there's no mod to be updated
+    if (ui->modTreeWidget->topLevelItemCount() == 0) {
+        m_no_updates = true;
+    } else {
+        // FIXME: Find a more efficient way of doing this!
+
+        // Sort major items in alphabetical order (also sorts the children unfortunately)
+        ui->modTreeWidget->sortItems(0, Qt::SortOrder::AscendingOrder);
+
+        // Re-sort the children
+        auto* item = ui->modTreeWidget->topLevelItem(0);
+        for (int i = 1; item != nullptr; ++i) {
+            item->sortChildren(0, Qt::SortOrder::DescendingOrder);
+            item = ui->modTreeWidget->topLevelItem(i);
+        }
+    }
+
+    if (m_aborted || m_no_updates)
+        QMetaObject::invokeMethod(this, "reject", Qt::QueuedConnection);
+}
+
+// Part 1: Ensure we have a valid metadata
+auto ModUpdateDialog::ensureMetadata() -> bool
+{
+    auto index_dir = indexDir();
+
+    SequentialTask seq(m_parent, tr("Looking for metadata"));
+
+    // A better use of data structures here could remove the need for this QHash
+    QHash<QString, bool> should_try_others;
+    QList<Mod*> modrinth_tmp;
+    QList<Mod*> flame_tmp;
+
+    bool confirm_rest = false;
+    bool try_others_rest = false;
+    bool skip_rest = false;
+    ModPlatform::Provider provider_rest = ModPlatform::Provider::MODRINTH;
+
+    auto addToTmp = [&](Mod* m, ModPlatform::Provider p) {
+        switch (p) {
+            case ModPlatform::Provider::MODRINTH:
+                modrinth_tmp.push_back(m);
+                break;
+            case ModPlatform::Provider::FLAME:
+                flame_tmp.push_back(m);
+                break;
+        }
+    };
+
+    for (auto candidate : m_candidates) {
+        auto* candidate_ptr = candidate.get();
+        if (candidate->status() != ModStatus::NoMetadata) {
+            onMetadataEnsured(candidate_ptr);
+            continue;
+        }
+
+        if (skip_rest)
+            continue;
+
+        if (confirm_rest) {
+            addToTmp(candidate_ptr, provider_rest);
+            should_try_others.insert(candidate->internal_id(), try_others_rest);
+            continue;
+        }
+
+        ChooseProviderDialog chooser(this);
+        chooser.setDescription(tr("This mod (%1) does not have a metadata yet. We need to create one in order to keep relevant "
+                                  "information on how to update this "
+                                  "mod. To do this, please select a mod provider from which we can search for updates for %1.")
+                                   .arg(candidate->name()));
+        auto confirmed = chooser.exec() == QDialog::DialogCode::Accepted;
+
+        auto response = chooser.getResponse();
+
+        if (response.skip_all)
+            skip_rest = true;
+        if (response.confirm_all) {
+            confirm_rest = true;
+            provider_rest = response.chosen;
+            try_others_rest = response.try_others;
+        }
+
+        should_try_others.insert(candidate->internal_id(), response.try_others);
+
+        if (confirmed)
+            addToTmp(candidate_ptr, response.chosen);
+    }
+
+    if (!modrinth_tmp.empty()) {
+        auto* modrinth_task = new EnsureMetadataTask(modrinth_tmp, index_dir, ModPlatform::Provider::MODRINTH);
+        connect(modrinth_task, &EnsureMetadataTask::metadataReady, [this](Mod* candidate) { onMetadataEnsured(candidate); });
+        connect(modrinth_task, &EnsureMetadataTask::metadataFailed, [this, &should_try_others](Mod* candidate) {
+            onMetadataFailed(candidate, should_try_others.find(candidate->internal_id()).value(), ModPlatform::Provider::MODRINTH);
+        });
+        seq.addTask(modrinth_task);
+    }
+
+    if (!flame_tmp.empty()) {
+        auto* flame_task = new EnsureMetadataTask(flame_tmp, index_dir, ModPlatform::Provider::FLAME);
+        connect(flame_task, &EnsureMetadataTask::metadataReady, [this](Mod* candidate) { onMetadataEnsured(candidate); });
+        connect(flame_task, &EnsureMetadataTask::metadataFailed, [this, &should_try_others](Mod* candidate) {
+            onMetadataFailed(candidate, should_try_others.find(candidate->internal_id()).value(), ModPlatform::Provider::FLAME);
+        });
+        seq.addTask(flame_task);
+    }
+
+    seq.addTask(m_second_try_metadata);
+
+    ProgressDialog checking_dialog(m_parent);
+    checking_dialog.setSkipButton(true, tr("Abort"));
+    checking_dialog.setWindowTitle(tr("Generating metadata..."));
+    auto ret_metadata = checking_dialog.execWithTask(&seq);
+
+    return (ret_metadata != QDialog::DialogCode::Rejected);
+}
+
+void ModUpdateDialog::onMetadataEnsured(Mod* mod)
+{
+    // When the mod is a folder, for instance
+    if (!mod->metadata())
+        return;
+
+    switch (mod->metadata()->provider) {
+        case ModPlatform::Provider::MODRINTH:
+            m_modrinth_to_update.push_back(mod);
+            break;
+        case ModPlatform::Provider::FLAME:
+            m_flame_to_update.push_back(mod);
+            break;
+    }
+}
+
+ModPlatform::Provider next(ModPlatform::Provider p)
+{
+    switch (p) {
+        case ModPlatform::Provider::MODRINTH:
+            return ModPlatform::Provider::FLAME;
+        case ModPlatform::Provider::FLAME:
+            return ModPlatform::Provider::MODRINTH;
+    }
+
+    return ModPlatform::Provider::FLAME;
+}
+
+void ModUpdateDialog::onMetadataFailed(Mod* mod, bool try_others, ModPlatform::Provider first_choice)
+{
+    if (try_others) {
+        auto index_dir = indexDir();
+
+        auto* task = new EnsureMetadataTask(mod, index_dir, next(first_choice));
+        connect(task, &EnsureMetadataTask::metadataReady, [this](Mod* candidate) { onMetadataEnsured(candidate); });
+        connect(task, &EnsureMetadataTask::metadataFailed, [this](Mod* candidate) { onMetadataFailed(candidate, false); });
+
+        m_second_try_metadata->addTask(task);
+    } else {
+        QString reason{ tr("Didn't find a valid version on the selected mod provider(s)") };
+
+        m_failed_metadata.append({mod, reason});
+    }
+}
+
+void ModUpdateDialog::appendMod(CheckUpdateTask::UpdatableMod const& info)
+{
+    auto item_top = new QTreeWidgetItem(ui->modTreeWidget);
+    item_top->setCheckState(0, Qt::CheckState::Checked);
+    item_top->setText(0, info.name);
+    item_top->setExpanded(true);
+
+    auto provider_item = new QTreeWidgetItem(item_top);
+    provider_item->setText(0, tr("Provider: %1").arg(ProviderCaps.readableName(info.provider)));
+
+    auto old_version_item = new QTreeWidgetItem(item_top);
+    old_version_item->setText(0, tr("Old version: %1").arg(info.old_version.isEmpty() ? tr("Not installed") : info.old_version));
+
+    auto new_version_item = new QTreeWidgetItem(item_top);
+    new_version_item->setText(0, tr("New version: %1").arg(info.new_version));
+
+    auto changelog_item = new QTreeWidgetItem(item_top);
+    changelog_item->setText(0, tr("Changelog of the latest version"));
+
+    auto changelog = new QTreeWidgetItem(changelog_item);
+    auto changelog_area = new QTextBrowser();
+
+    switch (info.provider) {
+        case ModPlatform::Provider::MODRINTH: {
+            HoeDown h;
+            // HoeDown bug?: \n aren't converted to <br>
+            auto text = h.process(info.changelog.toUtf8());
+
+            // Don't convert if there's an HTML tag right after (Qt rendering weirdness)
+            text.remove(QRegularExpression("(\n+)(?=<)"));
+            text.replace('\n', "<br>");
+
+            changelog_area->setHtml(text);
+            break;
+        }
+        case ModPlatform::Provider::FLAME: {
+            changelog_area->setHtml(info.changelog);
+            break;
+        }
+    }
+
+    changelog_area->setOpenExternalLinks(true);
+    changelog_area->setLineWrapMode(QTextBrowser::LineWrapMode::NoWrap);
+    changelog_area->setVerticalScrollBarPolicy(Qt::ScrollBarPolicy::ScrollBarAsNeeded);
+
+    // HACK: Is there a better way of achieving this?
+    auto font_height = QFontMetrics(changelog_area->font()).height();
+    changelog_area->setMaximumHeight((changelog_area->toPlainText().count(QRegularExpression("\n|<br>")) + 2) * font_height);
+
+    ui->modTreeWidget->setItemWidget(changelog, 0, changelog_area);
+
+    ui->modTreeWidget->addTopLevelItem(item_top);
+}
+
+auto ModUpdateDialog::getTasks() -> const QList<ModDownloadTask*>
+{
+    QList<ModDownloadTask*> list;
+
+    auto* item = ui->modTreeWidget->topLevelItem(0);
+
+    for (int i = 1; item != nullptr; ++i) {
+        if (item->checkState(0) == Qt::CheckState::Checked) {
+            list.push_back(m_tasks.find(item->text(0)).value());
+        }
+
+        item = ui->modTreeWidget->topLevelItem(i);
+    }
+
+    return list;
+}

launcher/ui/dialogs/ModUpdateDialog.h

@@ -0,0 +1,62 @@
+#pragma once
+
+#include "BaseInstance.h"
+#include "ModDownloadTask.h"
+#include "ReviewMessageBox.h"
+
+#include "minecraft/mod/ModFolderModel.h"
+
+#include "modplatform/CheckUpdateTask.h"
+
+class Mod;
+class ModrinthCheckUpdate;
+class FlameCheckUpdate;
+class ConcurrentTask;
+
+class ModUpdateDialog final : public ReviewMessageBox {
+    Q_OBJECT
+   public:
+    explicit ModUpdateDialog(QWidget* parent,
+                             BaseInstance* instance,
+                             const std::shared_ptr<ModFolderModel> mod_model,
+                             QList<Mod::Ptr>& search_for);
+
+    void checkCandidates();
+
+    void appendMod(const CheckUpdateTask::UpdatableMod& info);
+
+    const QList<ModDownloadTask*> getTasks();
+    auto indexDir() const -> QDir { return m_mod_model->indexDir(); }
+
+    auto noUpdates() const -> bool { return m_no_updates; };
+    auto aborted() const -> bool { return m_aborted; };
+
+   private:
+    auto ensureMetadata() -> bool;
+
+   private slots:
+    void onMetadataEnsured(Mod*);
+    void onMetadataFailed(Mod*, bool try_others = false, ModPlatform::Provider first_choice = ModPlatform::Provider::MODRINTH);
+
+   private:
+    QWidget* m_parent;
+
+    ModrinthCheckUpdate* m_modrinth_check_task = nullptr;
+    FlameCheckUpdate* m_flame_check_task = nullptr;
+
+    const std::shared_ptr<ModFolderModel> m_mod_model;
+
+    QList<Mod::Ptr>& m_candidates;
+    QList<Mod*> m_modrinth_to_update;
+    QList<Mod*> m_flame_to_update;
+
+    ConcurrentTask* m_second_try_metadata;
+    QList<std::tuple<Mod*, QString>> m_failed_metadata;
+    QList<std::tuple<Mod*, QString, QUrl>> m_failed_check_update;
+
+    QHash<QString, ModDownloadTask*> m_tasks;
+    BaseInstance* m_instance;
+
+    bool m_no_updates = false;
+    bool m_aborted = false;
+};

launcher/ui/dialogs/ProgressDialog.cpp

@@ -62,24 +62,24 @@ void ProgressDialog::updateSize()
 int ProgressDialog::execWithTask(Task* task)
 {
     this->task = task;
-    QDialog::DialogCode result;
 
     if (!task) {
-        qDebug() << "Programmer error: progress dialog created with null task.";
+        qDebug() << "Programmer error: Progress dialog created with null task.";
-        return Accepted;
+        return QDialog::DialogCode::Accepted;
     }
 
+    QDialog::DialogCode result;
     if (handleImmediateResult(result)) {
         return result;
     }
 
     // Connect signals.
-    connect(task, SIGNAL(started()), SLOT(onTaskStarted()));
+    connect(task, &Task::started, this, &ProgressDialog::onTaskStarted);
-    connect(task, SIGNAL(failed(QString)), SLOT(onTaskFailed(QString)));
+    connect(task, &Task::failed, this, &ProgressDialog::onTaskFailed);
-    connect(task, SIGNAL(succeeded()), SLOT(onTaskSucceeded()));
+    connect(task, &Task::succeeded, this, &ProgressDialog::onTaskSucceeded);
-    connect(task, SIGNAL(status(QString)), SLOT(changeStatus(const QString&)));
+    connect(task, &Task::status, this, &ProgressDialog::changeStatus);
-    connect(task, SIGNAL(stepStatus(QString)), SLOT(changeStatus(const QString&)));
+    connect(task, &Task::stepStatus, this, &ProgressDialog::changeStatus);
-    connect(task, SIGNAL(progress(qint64, qint64)), SLOT(changeProgress(qint64, qint64)));
+    connect(task, &Task::progress, this, &ProgressDialog::changeProgress);
 
     connect(task, &Task::aborted, [this] { onTaskFailed(tr("Aborted by user")); });
 
@@ -89,19 +89,15 @@ int ProgressDialog::execWithTask(Task* task)
         ui->globalProgressBar->setHidden(true);
     }
 
-    // if this didn't connect to an already running task, invoke start
+    // It's a good idea to start the task after we entered the dialog's event loop :^)
     if (!task->isRunning()) {
-        task->start();
+        QMetaObject::invokeMethod(task, &Task::start, Qt::QueuedConnection);
-    }
-    if (task->isRunning()) {
-        changeProgress(task->getProgress(), task->getTotalProgress());
-        changeStatus(task->getStatus());
-        return QDialog::exec();
-    } else if (handleImmediateResult(result)) {
-        return result;
     } else {
-        return QDialog::Rejected;
+        changeStatus(task->getStatus());
+        changeProgress(task->getProgress(), task->getTotalProgress());
     }
+
+    return QDialog::exec();
 }
 
 // TODO: only provide the unique_ptr overloads

launcher/ui/dialogs/ReviewMessageBox.cpp

@@ -40,7 +40,7 @@ auto ReviewMessageBox::deselectedMods() -> QStringList
 
     auto* item = ui->modTreeWidget->topLevelItem(0);
 
-    for (int i = 0; item != nullptr; ++i) {
+    for (int i = 1; item != nullptr; ++i) {
         if (item->checkState(0) == Qt::CheckState::Unchecked) {
             list.append(item->text(0));
         }

launcher/ui/dialogs/ScrollMessageBox.ui

@@ -6,7 +6,7 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>400</width>
+    <width>500</width>
     <height>455</height>
    </rect>
   </property>

launcher/ui/pages/instance/ExternalResourcesPage.ui

@@ -147,6 +147,17 @@
     <string>Download a new resource</string>
    </property>
   </action>
+  <action name="actionUpdateItem">
+   <property name="enabled">
+    <bool>false</bool>
+   </property>
+   <property name="text">
+    <string>Check for &amp;Updates</string>
+   </property>
+   <property name="toolTip">
+    <string>"Tries to find / update all selected resources (all resources if none is selected)"</string>
+   </property>
+  </action>
  </widget>
  <customwidgets>
   <customwidget>

launcher/ui/pages/instance/ModFolderPage.cpp

@@ -49,6 +49,7 @@
 #include "ui/GuiUtil.h"
 #include "ui/dialogs/CustomMessageBox.h"
 #include "ui/dialogs/ModDownloadDialog.h"
+#include "ui/dialogs/ModUpdateDialog.h"
 
 #include "DesktopServices.h"
 
@@ -78,6 +79,23 @@ ModFolderPage::ModFolderPage(BaseInstance* inst, std::shared_ptr<ModFolderModel>
         ui->actionsToolbar->insertActionBefore(ui->actionAddItem, ui->actionDownloadItem);
 
         connect(ui->actionDownloadItem, &QAction::triggered, this, &ModFolderPage::installMods);
+
+        ui->actionUpdateItem->setToolTip(tr("Tries to find / update all selected mods (all mods if none is selected)"));
+        ui->actionsToolbar->insertActionAfter(ui->actionAddItem, ui->actionUpdateItem);
+        connect(ui->actionUpdateItem, &QAction::triggered, this, &ModFolderPage::updateMods);
+
+        connect(ui->treeView->selectionModel(), &QItemSelectionModel::selectionChanged, this,
+                [this] { ui->actionUpdateItem->setEnabled(ui->treeView->selectionModel()->hasSelection() || !m_model->empty()); });
+
+        connect(mods.get(), &ModFolderModel::rowsInserted, this,
+                [this] { ui->actionUpdateItem->setEnabled(ui->treeView->selectionModel()->hasSelection() || !m_model->empty()); });
+                
+        connect(mods.get(), &ModFolderModel::updateFinished, this, [this, mods] {
+            ui->actionUpdateItem->setEnabled(ui->treeView->selectionModel()->hasSelection() || !m_model->empty());
+
+            // Prevent a weird crash when trying to open the mods page twice in a session o.O
+            disconnect(mods.get(), &ModFolderModel::updateFinished, this, 0);
+        });
     }
 }
 
@@ -107,7 +125,6 @@ bool CoreModFolderPage::shouldDisplay() const
             return false;
         if (version->getComponent("net.minecraft")->getReleaseDateTime() < g_VersionFilterData.legacyCutoffDate)
             return true;
-        
     }
     return false;
 }
@@ -118,7 +135,7 @@ void ModFolderPage::installMods()
         return;
     if (m_instance->typeName() != "Minecraft")
         return;  // this is a null instance or a legacy instance
-    
+
     auto profile = static_cast<MinecraftInstance*>(m_instance)->getPackProfile();
     if (profile->getModLoaders() == ModAPI::Unspecified) {
         QMessageBox::critical(this, tr("Error"), tr("Please install a mod loader first!"));
@@ -140,7 +157,7 @@ void ModFolderPage::installMods()
             QStringList warnings = tasks->warnings();
             if (warnings.count())
                 CustomMessageBox::selectable(this, tr("Warnings"), warnings.join('\n'), QMessageBox::Warning)->show();
-            
+
             tasks->deleteLater();
         });
 
@@ -155,3 +172,58 @@ void ModFolderPage::installMods()
         m_model->update();
     }
 }
+
+void ModFolderPage::updateMods()
+{
+    auto selection = m_filterModel->mapSelectionToSource(ui->treeView->selectionModel()->selection()).indexes();
+
+    auto mods_list = m_model->selectedMods(selection);
+    bool use_all = mods_list.empty();
+    if (use_all)
+        mods_list = m_model->allMods();
+
+    ModUpdateDialog update_dialog(this, m_instance, m_model, mods_list);
+    update_dialog.checkCandidates();
+
+    if (update_dialog.aborted()) {
+        CustomMessageBox::selectable(this, tr("Aborted"), tr("The mod updater was aborted!"), QMessageBox::Warning)->show();
+        return;
+    }
+    if (update_dialog.noUpdates()) {
+        CustomMessageBox::selectable(this, tr("Update checker"),
+                                     (mods_list.size() == 1)
+                                         ? tr("'%1' is up-to-date! :)").arg(mods_list.front()->name())
+                                         : tr("All %1mods are up-to-date! :)").arg(use_all ? "" : (tr("selected") + " ")))
+            ->exec();
+        return;
+    }
+
+    if (update_dialog.exec()) {
+        ConcurrentTask* tasks = new ConcurrentTask(this);
+        connect(tasks, &Task::failed, [this, tasks](QString reason) {
+            CustomMessageBox::selectable(this, tr("Error"), reason, QMessageBox::Critical)->show();
+            tasks->deleteLater();
+        });
+        connect(tasks, &Task::aborted, [this, tasks]() {
+            CustomMessageBox::selectable(this, tr("Aborted"), tr("Download stopped by user."), QMessageBox::Information)->show();
+            tasks->deleteLater();
+        });
+        connect(tasks, &Task::succeeded, [this, tasks]() {
+            QStringList warnings = tasks->warnings();
+            if (warnings.count()) {
+                CustomMessageBox::selectable(this, tr("Warnings"), warnings.join('\n'), QMessageBox::Warning)->show();
+            }
+            tasks->deleteLater();
+        });
+
+        for (auto task : update_dialog.getTasks()) {
+            tasks->addTask(task);
+        }
+
+        ProgressDialog loadDialog(this);
+        loadDialog.setSkipButton(true, tr("Abort"));
+        loadDialog.execWithTask(tasks);
+
+        m_model->update();
+    }
+}

launcher/ui/pages/instance/ModFolderPage.h

@@ -56,6 +56,7 @@ class ModFolderPage : public ExternalResourcesPage {
 
    private slots:
     void installMods();
+    void updateMods();
 };
 
 class CoreModFolderPage : public ModFolderPage {

launcher/ui/pages/modplatform/flame/FlameModPage.cpp

@@ -64,7 +64,7 @@ FlameModPage::FlameModPage(ModDownloadDialog* dialog, BaseInstance* instance)
 auto FlameModPage::validateVersion(ModPlatform::IndexedVersion& ver, QString mineVer, ModAPI::ModLoaderTypes loaders) const -> bool
 {
     Q_UNUSED(loaders);
-    return ver.mcVersion.contains(mineVer);
+    return ver.mcVersion.contains(mineVer) && !ver.downloadUrl.isEmpty();
 }
 
 // I don't know why, but doing this on the parent class makes it so that

launcher/ui/widgets/WideBar.cpp

@@ -76,13 +76,20 @@ void WideBar::addSeparator()
     m_entries.push_back(entry);
 }
 
-void WideBar::insertActionBefore(QAction* before, QAction* action){
+auto WideBar::getMatching(QAction* act) -> QList<BarEntry*>::iterator
-    auto iter = std::find_if(m_entries.begin(), m_entries.end(), [before](BarEntry * entry) {
+{
-        return entry->wideAction == before;
+    auto iter = std::find_if(m_entries.begin(), m_entries.end(), [act](BarEntry * entry) {
+        return entry->wideAction == act;
     });
-    if(iter == m_entries.end()) {
+    
+    return iter;
+}
+
+void WideBar::insertActionBefore(QAction* before, QAction* action){
+    auto iter = getMatching(before);
+    if(iter == m_entries.end())
         return;
-    }
+
     auto entry = new BarEntry();
     entry->qAction = insertWidget((*iter)->qAction, new ActionButton(action, this));
     entry->wideAction = action;
@@ -90,14 +97,24 @@ void WideBar::insertActionBefore(QAction* before, QAction* action){
     m_entries.insert(iter, entry);
 }
 
+void WideBar::insertActionAfter(QAction* after, QAction* action){
+    auto iter = getMatching(after);
+    if(iter == m_entries.end())
+        return;
+
+    auto entry = new BarEntry();
+    entry->qAction = insertWidget((*(iter+1))->qAction, new ActionButton(action, this));
+    entry->wideAction = action;
+    entry->type = BarEntry::Action;
+    m_entries.insert(iter + 1, entry);
+}
+
 void WideBar::insertSpacer(QAction* action)
 {
-    auto iter = std::find_if(m_entries.begin(), m_entries.end(), [action](BarEntry * entry) {
+    auto iter = getMatching(action);
-        return entry->wideAction == action;
+    if(iter == m_entries.end())
-    });
-    if(iter == m_entries.end()) {
         return;
-    }
+
     QWidget* spacer = new QWidget();
     spacer->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
 
@@ -107,6 +124,18 @@ void WideBar::insertSpacer(QAction* action)
     m_entries.insert(iter, entry);
 }
 
+void WideBar::insertSeparator(QAction* before)
+{
+    auto iter = getMatching(before);
+    if(iter == m_entries.end())
+        return;
+
+    auto entry = new BarEntry();
+    entry->qAction = QToolBar::insertSeparator(before);
+    entry->type = BarEntry::Separator;
+    m_entries.insert(iter, entry);
+}
+
 QMenu * WideBar::createContextMenu(QWidget *parent, const QString & title)
 {
     QMenu *contextMenu = new QMenu(title, parent);

launcher/ui/widgets/WideBar.h

@@ -1,27 +1,34 @@
 #pragma once
 
-#include <QToolBar>
 #include <QAction>
 #include <QMap>
+#include <QToolBar>
 
 class QMenu;
 
-class WideBar : public QToolBar
+class WideBar : public QToolBar {
-{
     Q_OBJECT
 
-public:
+   public:
-    explicit WideBar(const QString &title, QWidget * parent = nullptr);
+    explicit WideBar(const QString& title, QWidget* parent = nullptr);
-    explicit WideBar(QWidget * parent = nullptr);
+    explicit WideBar(QWidget* parent = nullptr);
     virtual ~WideBar();
 
-    void addAction(QAction *action);
+    void addAction(QAction* action);
     void addSeparator();
-    void insertSpacer(QAction *action);
-    void insertActionBefore(QAction *before, QAction *action);
-    QMenu *createContextMenu(QWidget *parent = nullptr, const QString & title = QString());
 
-private:
+    void insertSpacer(QAction* action);
+    void insertSeparator(QAction* before);
+    void insertActionBefore(QAction* before, QAction* action);
+    void insertActionAfter(QAction* after, QAction* action);
+
+    QMenu* createContextMenu(QWidget* parent = nullptr, const QString& title = QString());
+
+   private:
     struct BarEntry;
-    QList<BarEntry *> m_entries;
+
+    auto getMatching(QAction* act) -> QList<BarEntry*>::iterator;
+
+   private:
+    QList<BarEntry*> m_entries;
 };

libraries/README.md

@@ -149,6 +149,12 @@ BSD licensed, derived from [QtSingleApplication](https://github.com/qtproject/qt
 
 Changes are made to make the code more generic and useful in less usual conditions.
 
+## murmur2
+
+Canonical implementation of the murmur2 hash, taken from [SMHasher](https://github.com/aappleby/smhasher).
+
+Public domain (the author disclaimed the copyright).
+
 ## optional-bare
 
 A simple single-file header-only version of a C++17-like optional for default-constructible, copyable types, for C++98 and later.

libraries/murmur2/CMakeLists.txt

@@ -0,0 +1,12 @@
+cmake_minimum_required(VERSION 3.9.4)
+project(murmur2)
+
+set(MURMUR_SOURCES
+    src/MurmurHash2.h
+    src/MurmurHash2.cpp
+)
+
+add_library(Launcher_murmur2 STATIC ${MURMUR_SOURCES})
+target_include_directories(Launcher_murmur2 PUBLIC ${CMAKE_CURRENT_SOURCE_DIR} "src" )
+
+generate_export_header(Launcher_murmur2)

libraries/murmur2/src/MurmurHash2.cpp

@@ -0,0 +1,86 @@
+//-----------------------------------------------------------------------------
+// MurmurHash2 was written by Austin Appleby, and is placed in the public
+// domain. The author hereby disclaims copyright to this source code.
+
+// Note - This code makes a few assumptions about how your machine behaves -
+
+// 1. We can read a 4-byte value from any address without crashing
+// 2. sizeof(int) == 4
+
+// And it has a few limitations -
+
+// 1. It will not work incrementally.
+// 2. It will not produce the same results on little-endian and big-endian
+//    machines.
+
+#include "MurmurHash2.h"
+
+//-----------------------------------------------------------------------------
+// Platform-specific functions and macros
+
+// Microsoft Visual Studio
+
+#if defined(_MSC_VER)
+
+#define BIG_CONSTANT(x) (x)
+
+// Other compilers
+
+#else	// defined(_MSC_VER)
+
+#define BIG_CONSTANT(x) (x##LLU)
+
+#endif // !defined(_MSC_VER)
+
+//-----------------------------------------------------------------------------
+
+uint64_t MurmurHash2 ( const void* key, int len, uint32_t seed )
+{
+  // 'm' and 'r' are mixing constants generated offline.
+  // They're not really 'magic', they just happen to work well.
+
+  const uint32_t m = 0x5bd1e995;
+  const int r = 24;
+
+  // Initialize the hash to a 'random' value
+
+  uint32_t h = seed ^ len;
+
+  // Mix 4 bytes at a time into the hash
+  const auto* data = (const unsigned char*) key;
+  while(len >= 4)
+  {
+    uint32_t k = *(uint32_t*)data;
+
+    k *= m;
+    k ^= k >> r;
+    k *= m;
+
+    h *= m;
+    h ^= k;
+
+    data += 4*sizeof(char);
+    len -= 4;
+  }
+
+  // Handle the last few bytes of the input array
+
+  switch(len)
+  {
+  case 3: h ^= data[2] << 16;
+  case 2: h ^= data[1] << 8;
+  case 1: h ^= data[0];
+      h *= m;
+  };
+
+  // Do a few final mixes of the hash to ensure the last few
+  // bytes are well-incorporated.
+
+  h ^= h >> 13;
+  h *= m;
+  h ^= h >> 15;
+
+  return h;
+} 
+
+//-----------------------------------------------------------------------------

libraries/murmur2/src/MurmurHash2.h

@@ -0,0 +1,30 @@
+//-----------------------------------------------------------------------------
+// MurmurHash2 was written by Austin Appleby, and is placed in the public
+// domain. The author hereby disclaims copyright to this source code.
+
+#pragma once
+
+//-----------------------------------------------------------------------------
+// Platform-specific functions and macros
+
+// Microsoft Visual Studio
+
+#if defined(_MSC_VER) && (_MSC_VER < 1600)
+
+typedef unsigned char uint8_t;
+typedef unsigned int uint32_t;
+typedef unsigned __int64 uint64_t;
+
+// Other compilers
+
+#else	// defined(_MSC_VER)
+
+#include <stdint.h>
+
+#endif // !defined(_MSC_VER)
+
+//-----------------------------------------------------------------------------
+
+uint64_t MurmurHash2        ( const void* key, int len, uint32_t seed = 1 );
+
+//-----------------------------------------------------------------------------